SES Light But No Stored Code???

[JAKE]

96 LT1, Auto

SES light began flashing then remained ON steady. Engine never missed a beat and NO difference in drivability. Yet, when I used the paper-clip method to determine the code, none was stored. Auto scanning showed - - -, in all modes so I can't trace the source.

I shut down and restarted the engine and SES light remained illuminated, but still no stored code. Next day, after car sat all night, same thing; light but NO code stored.

I know disconnecting the battery, etc., will clear the light issue but I'd like to know what's up that caused it.

Any ideas other than buying a scanner or hitting AutoZone?

Thanks,

Jake

West Point ROCKS!

 

[badglas]

SES light, no code stored

You need to get a FSM and run the flow chart for this symptom. Common in earlier C4's because of ECM failures. Not common in a 96. Use the flow chart, don't guess. I would suspect a bad PCM but that too is unusual for this car.

Ron Kane
Benchmark Corvette Service
www.benchmarkcorvetteservice.com

 

[Robertwav1]

I would check battery voltage. Battery could be going bad.

 

[Toms007]

Not 100% sure, but I don't think you can use the paper clip method on the 96's, as that began the OBDII. I think you have to have a code reader to pull codes from your car. :confused

 

[Hib Halverson]

You cannot use the "paper clip" method on a 96 because the ECM does not support "flash-code" diagnostics. 1993 was the last year for flash-code diagnostics on LT1s and 1995 was the last year for that for LT5 engines.

To get codes, you must either own a scan tester (either hardware-based or software-based) which supports OBD II diagnostics or take the car to a service facility which has that equipment.

If the MIL (check engine light) is flashing on a 96, that means there's a serious problem with engine controls which greatly increases the car's exhaust emissions. I'm going to guess that, since you've not noted any driveabiity issues, one or both cats have failed. Again, that's a guess not a solution. The only way to know what the problem is for sure is with a scan tester and the factory service manual.

Road test the car, see if the light flashes or comes on again, if it does, either buy a scan tester or take the car to a service facility which has one.

 

[Toms007]

Thanks Hib for verifying that, I was pretty sure that was the case.

 

[Hib Halverson]

You're welcome.

I just hope it's something less expensive than your cats.

Also, if you decide to look for a tester, the low-end consumer-grade stuff is often quite "iffy". Avoid a "code reader" unless you are on a super tight budget and just want it for reading codes and no other diagnostic purposes.

A couple years ago, for "Corvette Enthuaist" I evaluated several consumer scan testers and the only one I use which I can say was acceptable for an advanced DIY was made by Kal-Equip. Unfortunately, even that one was about 800 bucks.

But, don't cry to much, the professional-grade equipment (the once which do full diagnostics on all the cars on-board computers) are upwards of three grand.

 

[Vettelt193]

It is confusing on the 1996 because some of the codes are in there if you paper-clip it. The key is only the codes that are backwards compatible made it, so just because it reads nothing in the paper-clip method doesn't mean there are no codes.

 

[Hib Halverson]

The ECM in a 96 does not support flash-code diagnostics. You must use a scan tool for any engine controls diagnostics.

Other controllers, such as chassis, body, SIR and LTPWS may or may not. Consult the factory service manual for details.

 

[Schrade]

It is confusing on the 1996 because some of the codes are in there if you paper-clip it. .

Gotta' agree with ya' on that one uh huh. (not really confusing tho')

From here...

Sequenced Code Recovery - 1994 through 1996:
In 1994, Chevrolet went to a 16 pin ALDL connector in preparation for the federally mandated change to the much more capable OBD-II (On Board Diagnostics - Version 2) system.
As with the 1990-1993 model, you can display codes on the speedometer but the pins to be shorted are different:

Beginning in 1994, you short pin "12" to pin "4" and once again turn the ignition switch to "On" without starting the engine.
The speedometer will display any codes using the same protocol as the 1990-1993 model but there are some changes in the designation for the modules plus additional modules are added:
Module "1" is still the CCM module.
Module "4" is now called the PCM module (Powertrain Control Module) because automatic transmission computer control was added to Engine Control Module in 1994.
Module 7 (on the 1996 model only) is the RTD module. (This is the Real Time Dampening module which replaced the Selective Ride Control module in 1996).
Module 9 is the ABS/ASR module number from 1994 through 1996.
Finally, Module "A", the DERM (Dynamic Energy Control Module --- the air bag control module) will be requested to show any codes.
Just like the 1990-1993 display, you read the codes on the speedometer and read the module number on the trip odometer.
Again, you can cause the codes to repeat by turning the ignition off for five seconds and then back on.
Turn the ignition off and remove the short to restore normal operation.

 

[Hib Halverson]

It is true that you can display some fault codes on the IP display by using "CCM diagnostics", however, on a 96, since it's fully OBD2 compliant, you cannot display DTCs from the PCM because the IP display can only show two digits and the codes have four digits.

You can look at codes in other modules than but not those from module 4.