Why No More SES Light
Thread Starter
Instructor
Joined: Jun 2004
Posts: 247
Likes: 0
From: Derry nh
Why No More SES Light
My '91 L98 would always throw an EGR code since the EGR valve has been removed. The car recently died due to faulty (original) injectors and after being replaced it runs fine, even better that it used to, but fuel mileage is down by 25% and the SES doesn't come on any more. Something has changed and either the EGR test is not running now or it is and is passing. Don't know how either could happen but I think it's a definite clue to this mileage loss.
Any idea what components are involved when the ECM runs the EGR test?
Any idea what components are involved when the ECM runs the EGR test?
Thread Starter
Instructor
Joined: Jun 2004
Posts: 247
Likes: 0
From: Derry nh
But SES still lights when the bulb check runs while starting and will still flash the trouble codes, so no, the bulb isn't burned out.
Some condition or group of conditions is now causing either the EGR test not to be run or is causing it to pass (neat trick since there's no EGR or solenoid and the solenoid connector is sitting there unplugged.).
I'm convinced the recent lack of EGR code is somehow related to my recent low gas mileage.
Some condition or group of conditions is now causing either the EGR test not to be run or is causing it to pass (neat trick since there's no EGR or solenoid and the solenoid connector is sitting there unplugged.).
I'm convinced the recent lack of EGR code is somehow related to my recent low gas mileage.
Burning Brakes
Joined: Jan 2007
Posts: 853
Likes: 0
From: Slinger WI
I read somewhere, if you were to put some resistor, inplace of where the egr connects, will eliminate the ses. just a FYI. also what size of injectors did you install? many of right ups here, regarding this. do a search! may be as easy as ecm relearning.
Thread Starter
Instructor
Joined: Jun 2004
Posts: 247
Likes: 0
From: Derry nh
The shop claimed to match the existing injectors (which I was told by previous owner to be original) and checked with GM so put in 21# Accels. I hard-reset the ECM a few weeks ago and it did seem to learn (took a few days to start running better) the injectors. Mileage however is down 25% from before.
Here's what's been done/checked:
1) New 21# Accels (3 of the old ones were out-of-spec and 1 was wide open)
2) New AC Delco plugs, OEM
3) Timing checked and is 8 - 10 deg advanced
4) ECM reset by disconnecting battery and turning on headlights overnight
5) Temp Sensor checked via scan tool, reading 180deg while hot
6) O2 sensor checked via scan tool, is changing value up and down, system is in closed-loop operation
7) Tranny does lock up when it should
Car seems to run fine but mileage is terrible... it used to get 23-25 avg and 28-30 highway. Now gets 16-18 avg and 20-22 highway.
BTW car is a '91, L98, auto, slight mod cam, Hypertec chip, ignition module and 160 deg 'stat.
The ECM used to throw an EGR code (EGR hardware is missing) but now doesn't so I'm convinced that's a clue to the problem.
Here's what's been done/checked:
1) New 21# Accels (3 of the old ones were out-of-spec and 1 was wide open)
2) New AC Delco plugs, OEM
3) Timing checked and is 8 - 10 deg advanced
4) ECM reset by disconnecting battery and turning on headlights overnight
5) Temp Sensor checked via scan tool, reading 180deg while hot
6) O2 sensor checked via scan tool, is changing value up and down, system is in closed-loop operation
7) Tranny does lock up when it should
Car seems to run fine but mileage is terrible... it used to get 23-25 avg and 28-30 highway. Now gets 16-18 avg and 20-22 highway.
BTW car is a '91, L98, auto, slight mod cam, Hypertec chip, ignition module and 160 deg 'stat.
The ECM used to throw an EGR code (EGR hardware is missing) but now doesn't so I'm convinced that's a clue to the problem.
