GTS with CEL
07-28-2014, 12:55 PM
#1
Rennlist Member
Thread Starter
GTS with CEL
Hi all,
My 1993 GTS stuttered as it started yesterday (RPMs dropped to 400) and then threw a CEL. No other warning lights are involved. The car was Sharktuned about 5 years ago and has PEMs.
I'd like to retrieve the CEL codes. Does the ST/chips interfere with reading the blinking CEL process? I also have access to a Bosch Hammer. When I have used it in the past, many of the engine management functions were unavailable, presumably due to the ST. Lastly, will a ST2 read the CEL codes?
Thanks in advance!
My 1993 GTS stuttered as it started yesterday (RPMs dropped to 400) and then threw a CEL. No other warning lights are involved. The car was Sharktuned about 5 years ago and has PEMs.
I'd like to retrieve the CEL codes. Does the ST/chips interfere with reading the blinking CEL process? I also have access to a Bosch Hammer. When I have used it in the past, many of the engine management functions were unavailable, presumably due to the ST. Lastly, will a ST2 read the CEL codes?
Thanks in advance!
07-28-2014, 01:25 PM
#2
Rennlist Member
Craig,
I just answered your PM on the same subject:
If the ECU's have PEMs then the normal diagnostics are disabled, and replaced with the Sharktuner interface. The diag codes for the LH are pretty simple, mostly sensor faults, e.g. temp-II or MAF out of range, etc. Those are all monitored realtime with Sharktuner which provides for easy diagnosis.
Your car was Sharktuned, but the binfiles could have been copied to EPROMS and the PEMs replaced with the EPROMS. In that case the diagnostic functions will work as usual, and Sharktuner cannot be connected unless PEMs are again fitted (with the same binfile, either from a saved computer file or copied from the EPROMS with a PROM-programmer).
I would first have a look in the EZK or LH and confirm that PEMs. The troubleshooting section of the WSM details how to read out the CEL code, if EPROMS are fitted.
Poor running (stumbling etc) is usually an AFR problem, i.e. wrong fuel mixture as the result of a sensor going bad or an intermittent connection. The possible culprits are temp-II, NBO2 sensor, MAF. Try disconnecting the factory O2 sensor (rubber connector under/near the CE panel), if it runs better with the O2 sensor disconnected then that sensor is likely bad (e.g. shorted). The Temp-II sensor can be checked at the 35-pin LH connector, see the WSM. An aging MAF causes the mixture to get progressively leaner, the LH compensates (assuming a working O2 sensor) until it runs out of range. This is easily diagnosed with Sharktuner, and hard to diagnose otherwise.
How many miles since Jim tuned the car?
Cheers, Jim
I just answered your PM on the same subject:
If the ECU's have PEMs then the normal diagnostics are disabled, and replaced with the Sharktuner interface. The diag codes for the LH are pretty simple, mostly sensor faults, e.g. temp-II or MAF out of range, etc. Those are all monitored realtime with Sharktuner which provides for easy diagnosis.
Your car was Sharktuned, but the binfiles could have been copied to EPROMS and the PEMs replaced with the EPROMS. In that case the diagnostic functions will work as usual, and Sharktuner cannot be connected unless PEMs are again fitted (with the same binfile, either from a saved computer file or copied from the EPROMS with a PROM-programmer).
I would first have a look in the EZK or LH and confirm that PEMs. The troubleshooting section of the WSM details how to read out the CEL code, if EPROMS are fitted.
Poor running (stumbling etc) is usually an AFR problem, i.e. wrong fuel mixture as the result of a sensor going bad or an intermittent connection. The possible culprits are temp-II, NBO2 sensor, MAF. Try disconnecting the factory O2 sensor (rubber connector under/near the CE panel), if it runs better with the O2 sensor disconnected then that sensor is likely bad (e.g. shorted). The Temp-II sensor can be checked at the 35-pin LH connector, see the WSM. An aging MAF causes the mixture to get progressively leaner, the LH compensates (assuming a working O2 sensor) until it runs out of range. This is easily diagnosed with Sharktuner, and hard to diagnose otherwise.
How many miles since Jim tuned the car?
Cheers, Jim
07-28-2014, 01:57 PM
#3
Archive Gatekeeper
Rennlist Member
Rennlist Member
I stupidly put an LED bulb into the socket for the CEL when I did an LED retrofit on my '93. Since I just leave the PEMs in place, my solution to the problem (when the CEL was illuminating on startup) was to pull the gauge cluster and remove the bulb. 
07-28-2014, 04:55 PM
#4
Rennlist Member
Thread Starter
Rob: I replaced the CEL bulb with an LED several years ago. Until yesterday, CEL always seemed to behave normally: I'm pretty sure the light turned on with the key initially in position 1. After the engine started, the CEL light turned off. Is there some other behavior?
Thanks!
jcorenman: Thanks for you thoughts on this. The car has PEMS and tonight I will confirm that I am not able to put the dash in CEL diagnostic mode. After this diversion, I will start on the AFR issue that is probably driving all of this behavior.
It has been about 8000 miles and 4 years since it was last tuned. Thanks!
Thanks!
jcorenman: Thanks for you thoughts on this. The car has PEMS and tonight I will confirm that I am not able to put the dash in CEL diagnostic mode. After this diversion, I will start on the AFR issue that is probably driving all of this behavior.
It has been about 8000 miles and 4 years since it was last tuned. Thanks!
08-30-2014, 06:53 PM
#5
Rennlist Member
Thread Starter
Just a follow up on this CEL issue. I took the car out today. The CEL light was still lit and the engine still stuttered at WOT. I tried to read the CEL code and was unsuccessful in getting the system into the blinking mode. But I did manage to clear the CEL (somehow ... I wasn't trying). And the stuttering at WOT is gone. For now. Time will tell if I have an intermittent fault somewhere. In the meantime I will enjoy driving the car and start refreshing those pesky groundpoints. Thanks to those who offered advice.