Welcome to the Corvette Forums at the Corvette Action Center!

Help! Service Engine Light

nyliac

Member
Joined
Apr 20, 2008
Messages
7
Location
VA
Corvette
1995 Coupe
I have a 95 LT1, and the service engine light comes on intermitantly, especially after she's been running a bit, very hot outside, or going through a tunnel! My guess it has to do with the air intake, so I replaced the MAF sensor but it didnt fix the problem. Help if you can!
 
Service engine soon indicates a PCM code is set.

You can pull error codes by doing the following.

Use a piece of wire or paper clip and short pin 4 to pin 12 on the Diag. connector.

Diag. connector is located above drivers right knee and looks like this.

[01|02|03|04|05|06|07|08]
[09|10|11|12|13|14|15|16]

Short the two pins together then turn ignition to On. (Don't start the engine).

Look at the LCD on the dash cluster. It will cycle some numbers.

Module 1 are error codes for the CCM
Module 4 are error codes for the PCM
Module 9 are error codes for the ABS
Module A are error codes for the Air Bag System
 
First, I'll suggest that you stop stop throwing parts at the problem. Trial-and-error or guessing is usually not an effective repair strategy on a 95.

Second, get any fault codes set in memory using the procedure listed above.

Third, buy the Factory Service Manual, and follow the diagnosic/repair procedures listed for the code(s) you pull out of the PCM memory.
 
I'd have to agree with both above. Throwing new parts at the problem just costs you money. Do the logical thing and check for codes, then with the FSM it will lead you through the flow chart until you have diagnosed the problem.
 
Service engine soon indicates a PCM code is set.

You can pull error codes by doing the following.

Use a piece of wire or paper clip and short pin 4 to pin 12 on the Diag. connector.

Diag. connector is located above drivers right knee and looks like this.

[01|02|03|04|05|06|07|08]
[09|10|11|12|13|14|15|16]

Short the two pins together then turn ignition to On. (Don't start the engine).

Look at the LCD on the dash cluster. It will cycle some numbers.

Module 1 are error codes for the CCM
Module 4 are error codes for the PCM
Module 9 are error codes for the ABS
Module A are error codes for the Air Bag System

First, I'll suggest that you stop stop throwing parts at the problem. Trial-and-error or guessing is usually an effective repair strategy on a 95.

Second, get any fault codes set in memory using the procedure listed above.

Third, buy the Factory Service Manual, and follow the diagnosic/repair procedures listed for the code(s) you pull out of the PCM memory.

I'd have to agree with both above. Throwing new parts at the problem just costs you money. Do the logical thing and check for codes, then with the FSM it will lead you through the flow chart until you have diagnosed the problem.
I agree with everything above,Except whats Highlighted in RED!! But then again I'm not a Technical Writer for Internet & Print Media, I'm just a Illiterate Technician and Low Life Car Dealer!!:thumb:thumb:thumb
 
I agree with everything above,Except whats Highlighted in RED!! But then again I'm not a Technical Writer for Internet & Print Media, I'm just a Illiterate Technician and Low Life Car Dealer!!:thumb:thumb:thumb

Don't cut yourself short Junk ,I think your a pretty good Technican.And hell I don't know how you could possibly be a "low life car dealer' ya haven't sold one in ten years .;LOL
 
Don't cut yourself short Junk ,I think your a pretty good Technican.And hell I don't know how you could possibly be a "low life car dealer' ya haven't sold one in ten years .;LOL
OK. So I see everyone agrees to read the codes before spending $, and I'm right there with you all. I guess I didn't give enough information last night. I have an auto x-ray to read the codes, but when I plug in, it shows no error codes, and my guess is that since it doesn't stay on continuously they are not being stored in the ECM.

Along with the service light going on and off after she runs awhile, it hard starts at times and I don't know if it is related to the service light. I had my state inspection done, and informed my "emergency mechanic" of the problem, he said he would need to use the more complex code reader during a test drive to get a read on the codes. Any suggestions before I spend $ on diagnostic and installation of a potentially bad sensor?
 
Yeah,I've got a ?? Has the battery been Low and Jumped Off or has been charged recently?:confused:confused
 
No, It's a fairly new battery. I looked at a few other responses with a similar problem, and they reference the IAC or Temp sending unit. What are you thoughts?
 
I agree with everything above,Except whats Highlighted in RED!! But then again I'm not a Technical Writer for Internet & Print Media, I'm just a Illiterate Technician and Low Life Car Dealer!!:thumb:thumb:thumb

Touche!

It was a typo, uh, gmjunkie.
 
OK. So I see everyone agrees to read the codes before spending $, and I'm right there with you all. I guess I didn't give enough information last night. I have an auto x-ray to read the codes, but when I plug in, it shows no error codes, and my guess is that since it doesn't stay on continuously they are not being stored in the ECM.

Along with the service light going on and off after she runs awhile, it hard starts at times and I don't know if it is related to the service light. I had my state inspection done, and informed my "emergency mechanic" of the problem, he said he would need to use the more complex code reader during a test drive to get a read on the codes. Any suggestions before I spend $ on diagnostic and installation of a potentially bad sensor?
 
What kind of auto x-ray is it?

Some are not really scan testers.

Others do not support your model year.
 
It's an EZ-Link. It has a blue OBD II (for 1994-1995 GM OBD 1 w/16 pin connector). Will this work?
 
No, It's a fairly new battery. I looked at a few other responses with a similar problem, and they reference the IAC or Temp sending unit. What are you thoughts?
I was just curious,I've had a few in the past that have had a low battery that had been charged or jumped off that would act like yours with a intermittent light that wouldn't store a code,and I've had to disconnect the battery for 5 minutes, then reconnect battery to Reboot the ECM and then go from there!! Don't have a clue what caused it other than maybe a spike in power,or some AC ripple from a battery charger or weak diode in the alternator!!;shrug;shrug IAC valve or Temp sensor out of range can certainly cause one to start hard warm or cold depending on where it's out of range at! I'm not familiar with Auto X-Ray,does it have a Data Stream mode??I use a Snap-On MT 2500 with Trouble Shooter software.I've had to drive some for several miles sometimes with the scanner in Data Mode to finely find the root of the problem,Electronic Problems can really "Inhale"!!:hb:hb
I guess that my first plan of attack would be Disconnect the Battery,Check and Clean All Chassis Grounds,Engine Grounds,Check and Clean All fuses in fuse panel at Rt End of dash,Outside on Lt Splash shield in front of battery,and Main Fuse panel behind battery on Lt A Pillar!! Then I would check the Eye connector on the BIG Red wire on the alternator!!(I've had several that was not getting a good connection where the eye was crimped to the wire causing voltage spikes and scrambling the ECM!!) Then I would reconnect the battery and start the car and check how much AC voltage is slipping past the diodes in the alternator,and then go from there!!(1.5-2.0 V AC Max!!)Much more than that can cause the ECM to do weird things!!:upthumbs

PS Really shouldn't have any AC voltage slipping past the diodes,but most do have just a little!!:thumb
 
This gives me some things to try before going out and spending a bunch of $. I really do appreciate you taking the time to get these fixum ideas to me. I will go through them and let you know what the results were. Have a great 4th of July weekend GM!
Thanks,
NYLIAC
 
It's an EZ-Link. It has a blue OBD II (for 1994-1995 GM OBD 1 w/16 pin connector). Will this work?

That should support the OBDI part of the 95's ECM. That car also has "partial OBD II" capabillity which might be but probably is not supported by that tester, however, OBDI diagnostics will get the job done.
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Advertise with the Corvette Action Center!

Double Your Chances!

Our Partners

Back
Top Bottom