Help! Frankenstein 1994 LT1 C41 H41 H54

[barrett50cal]

So to introduce my car, I bought it to save it from being chopped down into a hot rod car for a cheap price. The only snag was the engine, harness, and ECM was not in the car.

Then I found a 95 LT1 from a firebird for next to nothing (I bought the whole car and parted it out.) and rebuilt pretty much the entire engine and bought new corvette parts for the entire front of the engine (accessory bracket, water pump, new opti, etc.).

Once I was able to find a engine wiring harness for my car, it was from a 1995 Corvette base. The harnesses seem to be the same but after plugging everything in the car refuses to start. It will crank endlessly. The fuel pump is not coming on, and I have no spark. When I pull the codes from the ECM I get mixed results. Most of the time it will pull as C41, but occasionally it will pull as C54 and H41

I've read through my FSM for the 94 car and cant find anything standing out as wrong, however when following the flowchart for the "pulling my hair out" thread my multimeter begins pulsing between and open circuit and continuous when tested the tan wire (800 CKT) against ground. Is this normal behaviour?

Also if anybody has the pages from a 95 FSM that shows the pinouts of the harness connectors C100A to C100C, C237, C238, and C239 (pages 8A-202-13, 8A-202-16, 8A-202-17, and 8A-202-18 in my FSM) I would really appreciate being able to compare them to the 94 harness.

Please help me get this car back on the road!

Thank you.

 

[barrett50cal]

Thank you so much for the references! You helped me confirm that the 94 and the 95 harnesses are identical (at least going into the car). So the harness wasn't a waste of money.

After some probing around checking for resistance I think my ECM might be bad, even though the firebird I got it from was running before I moved it to my car. When I check resistance on the Serial Data Line going into the ECM with the engine harness disconnected from the CCM, I get 1030 ohms to ground from the data line. Does this sound like I should replace the ECM?

 

[barrett50cal]

Are you using the Camaro PCM and if so did you have it reflashed for a Corvette program or
are the programs the same ?

I am using the Firebird PCM, and I haven't reflashed it yet, because my programmer can't communicate with the PCM. I am using a paper clip to pull the codes. C41 H41 and H54 are all module 1 codes.

Module 4 gives: Err
Module 9 gives: ---
Module A gives: Err

What I'm not positive about is a guy on a website shows a 95 Camaro PCM shows pin A25 on the
PCM as the Fuel Enable signal sent to the PCM. The Corvette uses a password exchange
on the Serial Line for the Fuel Enable signal.

This looks like it might give me some serious problems enabling the fuel pump once I get the PCM working. Is the password just something that reflashing the PCM will fix, or is the password specific to my car's CCM?

 

[barrett50cal]

The SES light occassionally would come on and stay on at times. Other times it never would come on.

The PCM was for the engine that came from the firebird (it was a trans am). So it was definitely for an lt1.

Between your knowledge and the fact that the serial data line on the PCM itself (disconnected from the rest of the car) grounds out with 1000 ohms, I'm convinced my PCM is bad. Maybe it was knocked off the car when I wasn't around or something, since I share the garage I'm working in with my dad? I think I'll get one on order that will be flashed for the corvette already. I'll post back once I get it installed with my results.

Thank you for all of your help.

 

[barrett50cal]

Sorry for the late reply, life has been busy the past few days.

I checked all the grounds with a very good analog multimeter, and got continuous grounds on all of those pins.
Would these symptoms be present if any of the pins from the computer have been shorted out? I'm worried that after looking back over the harness there are 3 wires at the rear of the engine that were bare. It looks like the connector has been ripped off the harness.

On a side note is there and physical hardware difference between the F-body ECM's and the Y-body ECM's? The seller on ebay says that they can't flash the $EE bin onto the ECM's they have because there is a difference in the computers.

 

[ecss]

From my understanding the 16181333 was the PCM the Corvette's used. Camaros and Firebirds used a 16188051. I have read people say both will work on either vehicle.

That's one of the reasons I mentioned the Corvette used a serial bus for the fuel enable signal and the Camaror and Firebird's use a Theft Deterrent Module.

I've only read on one web-site saying the difference was the Corvette PCM had an extra chip for OBDII emulation. 94-95 Corvettes had some OBDII error codes not sure if the Firebird's did.

I thought $EE was a program / definition file that read the specific vehicle engine calibration binary file.
Another words each engine calibration file is car specific. Timing curve trans shift points for auto trans. shift quality fuel calibration etc...

I've seen some bin files for a Corvette 6 speed and for an auto on a web-site I'll try to post when I find it.

The fact you can't communicate with the PCM with your flash program indicates the PCM is bad or the program in the flash memory is corrupt. All you should need is power to the PCM to communicate with it through the 16 pin diag connector.

What program are you using and have you every seen the program and cable work before?

16188051 and 16181333 PCM Information $EE $EEB

Also read the first thread below.
http://www.camaroz28.com/forums/com...g-36/running-corvette-bin-567049/#post5073346

 

[barrett50cal]

Thank you for the links.

I was trying to use WinFlash from tunercats (free trial) to read the bin off of the firebird ecm to prove communication works. But of course it didn't work like I hoped.

The cable is actually a unbranded OBD multi-protocol adapter with a OBD2 serial cable attached. I don't know specifically if it will work with an OBD1 computer, but I have a USB to Serial adapter I plan on using if the CCM can communicate and my laptop can't. If I understand the way the car works, my laptop needs to have a Tx line from the serial connector connected to the 800 CKT tan wire in the diagnostic connector to flash files and a Rx line to read files. Kinda like this DIY: How To: Scan your OBD1 6.5 for less than $10! - Diesel Place : Chevrolet and GMC Diesel Truck Forums

I'm thinking I might be stuck ordering a F-body ECM and flashing it myself, since the price difference is about $100, at least from what I've found. Once I get the thing running I still have tires to replace, paint to redo, and college to try to pay for.

 

[ecss]

Okay I looked at Winflash. That won't work because it's for OBDII computers.

If you can get a ALDL to USB cable working you can purchase the Basic Tuner
software and the $EE definition file for $90.00 sent to you via E-mail. They also
offer a 30 down free trial version downloadable for 30 days. Not sure if this is
fully functional or just a demo type program. For your use you would still
need the $EE definition file which I'm positive does not come with the demo
program.

Or you can get this for only $160.00.

If you want the 12 pin diag connector Kit LT1 Tune 1
If you want the 16 pin diag connector kit LT1 Tune 2
If you want the kit with the cable that does both 12 or 16 pin LT1 Tune Y $185.00

The kit comes with cable ALDL to USB.
Tuner Software to allow you to modify parameters and the software to read and reprogram the PCM.
It also comes with the $EE definition file which allows you to read the engine calibration bin file.

Plug and Play.

 

[ecss]

Here's a link to 3 Corvette bin files you can download.

16188051 and 16181333 PCM Information $EE $EEB

 

[barrett50cal]

Long time status update!

So I bought a lt1 PCM programmed for my car off of ebay for $200. While I was waiting on it I went through the engine harness and found a few issues and corrected them. G107 was the bare wires at the back of the engine. I repaired the ground and bolted it to the block.

One of the O2 sensors leads had been pinched and the wire was broke all the way through. I soldered and heat shrinked these back together.

When I got my PCM, I plugged it in, hooked the battery up, and hoped for the best... Still no good. I ran through the codes again and of course H41 pops back up on module 1.
Module 4 is ---
Module 9 is H63 H64 H72
Module A is ERR.

I still don't have spark, or fuel injector signals. But I do have the fuel pump coming on and pressurizing the rail.

I'm seriously at a loss on what to do about this car now.

 

[ecss]

Long time status update!

So I bought a lt1 PCM programmed for my car off of ebay for $200. While I was waiting on it I went through the engine harness and found a few issues and corrected them. G107 was the bare wires at the back of the engine. I repaired the ground and bolted it to the block.

One of the O2 sensors leads had been pinched and the wire was broke all the way through. I soldered and heat shrinked these back together.

When I got my PCM, I plugged it in, hooked the battery up, and hoped for the best... Still no good. I ran through the codes again and of course H41 pops back up on module 1.
Module 4 is ---
Module 9 is H63 H64 H72
Module A is ERR.

I still don't have spark, or fuel injector signals. But I do have the fuel pump coming on and pressurizing the rail.

Module 1 (CCM) error 41 indicates a communication problem from the CCM to the PCM

Strange because
Module 4 ----- indicates the CCM can communicate with the PCM and there are no errors.

Are you jumpering the starter enable relay?
If so remove the jumper.


Module 9 (ABS/TSC) H72 indicates a communications error with the CCM H63 is a Valve Power Supply Malfunction. 64 is a Throttle Position Signal Malfunction.
Module A (Airbag)) err indicates no communications with the DERM.

Questions.

1) What part number PCM did you get?
2) Did they tell you what bin file the PCM is programmed for?
3) With both doors closed, when you insert the key and turn the ignition to On. What does the Security Light in the Dash Cluster do? Normal sequence should be the light goes on then Off.

4) Is the Service ASR and Service ABS stay On?

5) Does the Air Bag light flash 7 times then go Out?

 

[barrett50cal]

1) What part number PCM did you get?

Unfortunately all I was able to get was the 16188051. Money issues as a new college student.

2) Did they tell you what bin file the PCM is programmed for?

They didn't tell me what bin, however they took my tire size, car year, and eliminated EGR, VATS, and other emissions stuff.

3) With both doors closed, when you insert the key and turn the ignition to On. What does the Security Light in the Dash Cluster do? Normal sequence should be the light goes on then Off.

The light comes on with all of the other light and then goes off like it should. However, about once every 10 seconds of so the security light will flash on very briefly (about a quarter of a second) and the go back off. When this happens the dash also blinks SYS three times.

4) Is the Service ASR and Service ABS stay On?

The service ASR light stays on, but the service ABS light goes out.

5) Does the Air Bag light flash 7 times then go Out?

Yes.

After about 5 minutes the check engine soon light will go off and wont come back on unless I turn the key to off.
After about 2 minutes the blower kicks in for the HVAC controls.
The lights will never turn themselves off. I have to unplug the battery when I leave it, otherwise the lights will run it dead.

One thing I just realized is that the car doesn't ding or buzz with the key in the ignition and the doors open. I don't know the behavior for this exactly, but the car has never dinged or buzzed about anything.

Also I am just using the key for the starter. The starter turns over, so I assume the relay is working.

 

[ecss]

Unfortunately all I was able to get was the 16188051. Money issues as a new college student.

I'm still not convinced the two PCM's are identical. ;squint:

The Security light comes on with all of the other light and then goes off like it should. However, about once every 10 seconds of so the security light will flash on very briefly (about a quarter of a second) and the go back off. When this happens the dash also blinks SYS three times.

This could indicate the password exchange for Fuel Enable has failed. But if it has it should set a CCM 54.

The service ASR light stays on, but the service ABS light goes out.

I wouldn't be concerned about the ASR at the moment.

After about 5 minutes the check engine soon light will go off and wont come back on unless I turn the key to off.

If you turn turn the ignition On and do not crank the engine, the Service Engine Soon light should stay On.
Are you saying the Light goes out when the ignition is On and you don't crank the engine?

After about 2 minutes the blower kicks in for the HVAC controls.

That is normal if you reconnect the battery. The AC programmer recalibrates the blend door position.

The lights will never turn themselves off. I have to unplug the battery when I leave it, otherwise the lights will run it dead.

You sure the headlight dimmer isn't turning the interior lights On?
Otherwise when you have the ignition On and open one of the doors, does the door ajar light come On?

If it does, does the door Ajar light go out if you shut the door? The Door Ajar switch is located on the back edge of each door.

You could also insert the door key into each door. Rotate the door key and lock and unlock each door. Make sure when you remove the key the key cylinder is in the vertical position.

One thing I just realized is that the car doesn't ding or buzz with the key in the ignition and the doors open. I don't know the behavior for this exactly, but the car has never dinged or buzzed about anything.

The chime module is known to be flaky. It's not causing the no start problem.

One thing that bothers me is you have no spark. Do you have the old optispark?

If you do, you can attach the power and signal plug into the old optispark and if you turn the ignition On and with your hand manually rotate the optispark you should get a spark from the coil.


Are you positive you reattached all of the ground wires located at the bottom driver side bell housing stud?

Did you get your scanner cable working? The software you were using before was for OBDII you need OBD1 software. If you can get that you could see if you can communicate with the PCM which could help to identify what's going on with the PCM.

 

[Hib Halverson]

Y-car (along with C-car, H-car and U-van platforms) for MY94 and MY95 was part of GM's "early roll-out" of OBDII diagnostics. The car's original harness may have had a 16-pin connector and the ECM had OBD and partial OBDII capability.

F-car for MY95 (along with g-car, s/t-truck and j-car) was, also, part of the early roll-out of OBDII. A 95 F-car likely had a 16-pin connector with both OBD diagnostics and partial OBDII diagnostics.

The level of partial OBDII in MY95 was higher than was the partial OBDII for MY 94.

In 94/95 Y-ca and 95 F-car, only OBD fault codes would turn the MIL on. If OBDII codes were set the only way to get them was with a scan tester (back then it was the Vetronix TECH1A) having the proper software. At the time, GM's strategy was to field test some of the OBDII diagnostics 2-yrs (in the case of Corvette) and one year (in the case of F-car) before Federal law mandated OBDII diagnostics for the 1996 model year.

ECMs for a 94-Y and a 95-F cannot not flash the MIL for ECM fault codes.

I post this because the partial OBDII capability of the two ECMs in question, may or may not be playing a part in the trouble "barrett50cal" is having.

I'd have to do a little more research into Service Manuals but I seem to recall that when one did an ECM change on a late C4, reprogramming of either the ECM or the CCM or both was required before the car would run.

 

[barrett50cal]

If you turn turn the ignition On and do not crank the engine, the Service Engine Soon light should stay On.
Are you saying the Light goes out when the ignition is On and you don't crank the engine?

Yeah. The after a few minutes the only light on my info console is the Service ASR light. If I turn the key off and back on the Service engine light comes back on for a few minutes.

You sure the headlight dimmer isn't turning the interior lights On?Otherwise when you have the ignition On and open one of the doors, does the door ajar light come On?


If it does, does the door Ajar light go out if you shut the door? The Door Ajar switch is located on the back edge of each door.

My door ajar light is on. It doesn't go off with both of the doors shut, or with me and my dad manually pressing the door switches in.

One thing that bothers me is you have no spark. Do you have the old optispark?


If you do, you can attach the power and signal plug into the old optispark and if you turn the ignition On and with your hand manually rotate the optispark you should get a spark from the coil.

I plugged my old optispark in and had my dad spin the distributor. His entire arm went numb for about 10 minutes. (He shouldn't have been touching the car ) The coil definitely can give a good spark. Maybe the new optispark is bad/not spinning?

Are you positive you reattached all of the ground wires located at the bottom driver side bell housing stud?

I have three ring terminals, the negative battery cable, and a chassis strap going to the bell housing stud. One ground (G107) is bolted at the back of the intake. One ground (I don't know) is bolted to the frame on the passenger side. It is in the wire loom with the blower wires.

Did you get your scanner cable working? The software you were using before was for OBDII you need OBD1 software. If you can get that you could see if you can communicate with the PCM which could help to identify what's going on with the PCM.

I didn't get the computer scanner working, but I now have access to an OTC 4000e Pathfinder 1995 scanner (similar to this Nice OTC Domestic Pathfinder 2 Montior 4000E with Carrying Case and Manuals | eBay) with GM module pack. I still need to read through the book that it has with it.

@Hib Halverson
Most of what you said kinda went over my head. Are you saying that the computer is possibly giving OBDII codes?

Unfortunately this project is going to be drug out longer than I had hoped. I have to move into college the 12th (tomorrow), so any time I have to work on it will be breaks. My dad is going to continue to try to make it run, but we're both lost on why it won't work.

 

[ecss]

With the ignition On the Service Engine Soon indicator should be on solid all the time.

You are saying both PCM's have the problem with the Service Engine Soon indicator going on and then off with the ignition On?

The PCM is what controls the light. It grounds the bulb to turn it on.
To eliminate it's not the 12 volts going to the bulb causing it to go out some times. Verify when the bulb goes off is the Battery charge indicator bulb still On which should always stay On when the engine is not running? If both bulbs go out at the same time, some thing is wrong with the 12 volts.
If only the Check Engine Soon indicator goes out that points to a problem with the PCM.

Strange both door switches don't work.
When you open the door, the switch contacts close which provides a ground signal to the CCM which lights the door ajar indicator when the ignition is On.

Also if either door is open, the Security light on the dash cluster should flash.
If you close both doors the Security light should go out. This is with the ignition OFF. Does the Security light behave this way? I'm assuming the Security light always blinks because the CCM thinks the doors are always open.

To remove one of the door switches you need to remove one of the two screws and loosen the other one.
Rotate the body of the switch so you reinstall the screw you removed. This will keep the retainer plate inside the door frame in place. Then remove the other screw and pull the switch out and hopefully get to the harness plug. Unplug the two wire connector. With the plunger out you should read zero ohms across the two switch terminals. With the plunger pushed in you should read infinity. If you disconnect both door switches the Door Ajar indicator should go off.

Also on the passenger side of the engine compartment near the blower motor is a Buffer box for the Throttle body Position sensor used by the ABS/ASR. Did you plug the proper cable into that module?

Last thing is yes the new Optispark is either bad or not rotating.

 

[barrett50cal]

You are saying both PCM's have the problem with the Service Engine Soon indicator going on and then off with the ignition On?

Yes, after a few minutes the SES light goes off.

Strange both door switches don't work.
When you open the door, the switch contacts close which provides a ground signal to the CCM which lights the door ajar indicator when the ignition is On.

I took the switches off the car and tested them. The switches are normally closed (zero ohms across the switch until the switch is pressed). One side of the switch connector is continuous to ground.

Also if either door is open, the Security light on the dash cluster should flash.
If you close both doors the Security light should go out. This is with the ignition OFF. Does the Security light behave this way? I'm assuming the Security light always blinks because the CCM thinks the doors are always open.

This is not true. The security light blinks roughly once every ten seconds. The same time the SYS light blinks on the digital part of the dash.

Also on the passenger side of the engine compartment near the blower motor is a Buffer box for the Throttle body Position sensor used by the ABS/ASR. Did you plug the proper cable into that module?

I think so. It is plugged in.


I measured this connector against ground. I think it is a courtesy light that is connected to the kick panels. It's on both sides of the car under the dash.

Both sides of the connector measured zero ohms to ground.

The PCM is what controls the light. It grounds the bulb to turn it on.
To eliminate it's not the 12 volts going to the bulb causing it to go out some times. Verify when the bulb goes off is the Battery charge indicator bulb still On which should always stay On when the engine is not running? If both bulbs go out at the same time, some thing is wrong with the 12 volts.
If only the Check Engine Soon indicator goes out that points to a problem with the PCM.

When the check engine light goes out, the only light left on is the Service ASR light. The charge battery light does come on to begin with, but goes out with SES light. The only light that remains on after a few minutes of ignition on is the Service ASR light.

I also got to try the OTC 4000e Pathfinder. I tried to get the data stream on the CCM, the PCM, and the ABS/ASR. All three communications failed.

 

[ecss]

Yes, after a few minutes the SES light goes off.

That's not normal. SES should stay on solid with the ignition On and engine not running.

I took the switches off the car and tested them. The switches are normally closed (zero ohms across the switch until the switch is pressed). One side of the switch connector is continuous to ground.

The above is normal and are working.

This is not true. The security light blinks roughly once every ten seconds. The same time the SYS light blinks on the digital part of the dash.

The above is not normal. With doors open, the Security light should blink about once a second. SYS blinks if the CCM detects an electrical problem.

I measured this connector against ground. I think it is a courtesy light that is connected to the kick panels. It's on both sides of the car under the dash.

That connector is for the footwell light. With a volt meter red probe to the Orange wire and Black probe to the White wire you should measure 12 volts when the interior lights are on.
.

When the check engine light goes out, the only light left on is the Service ASR light. The charge battery light does come on to begin with, but goes out with SES light. The only light that remains on after a few minutes of ignition on is the Service ASR light.

The above is not normal. The battery charge indicator which is driven by the alternator regulator should always be on with the engine not running and ignition On. That's a very simple circuit. If you look at the alternator plug connector there is a Brown wire. The regulator grounds the Brown wire which goes to one side of the battery charge indicator bulb. The other side of the bulb has a constant 12 volts when the ignition switch is in run or start. It should never go off if the engine is not running. The Brown wire from the Alternator passes thru connector C100 C Pin E3. With all the electrical indicator problems you have, something is wired wrong.

Verify the Brown wire from the alternator plug is going to C100 C Pin E3. This is the Engine harness plug.
If you unplug the connector at the Alternator and turn the ignition On, the charge indicator should not be on.

Did you resolve the no spark problem from the Optispark?

h

 

[ecss]

One other thing I noticed, is it possible you have C238 and the plug for C239 reversed?
Both are 10 pin plugs.

 

[barrett50cal]

One other thing I noticed, is it possible you have C238 and the plug for C239 reversed?
Both are 10 pin plugs.

I really don't think they're mixed up. One's blue and ones white, correct? Blue to blue and white to white.

Did you resolve the no spark problem from the Optispark?

We haven't touched the engine again yet (mostly because I'm at college and home for like a day at a time every other week), but I think it's very probable that the optispark simply isn't turning.

The CCM still reads a code of H41 all the time and occasionally it will throw a C41 for like a second.

That connector is for the footwell light. With a volt meter red probe to the Orange wire and Black probe to the White wire you should measure 12 volts when the interior lights are on.

Should both sides of this connector be continuous to ground with the battery unplugged?

If you unplug the connector at the Alternator and turn the ignition On, the charge indicator should not be on.

This is how the light behaves when the alternator is unplugged. There are two brown wires coming off the alternator plug. Does one of them feed something else?

What is the odds of the CCM being dead? Is there a way that I can test it or take it to a company to test it? I'd hate for it to be a dead CCM, but I'd hate it even more if I bought a working one and that wasn't it.
Also as far as programming the CCM, is that just for mileage and VIN number?