88' IROC-Z
When I turn the key to on/engine off the SES light begins to flash slowly, after a few seconds it double the flash rate, if i sart the engine, it (the engine) runs rough, will cut-out if given throttle, and the SES light continues to flash at the same rate. I can also hear the vapor canister solenoid clicking at the same rate.

Anyone have a clue at to what's going on? I couldn't find any reference to the SES flashing like that in my manual?

No, the ALDL terminals are not jumpered, (if you're thinking I, or someone else had left it in diag mode.)

 

Have you jumpered pins "A" & "B" on the ALDL to see if any codes were stored in the computer. That would be one of the most logical points to start.

The Trickster!!!!!!!!!!!!!!

 

I didn't want to do that until I was sure that it would override the continious flash, and not fry my ECM.

I have yet to see any post on a continious flashing SES light with or without the ALDL jumpered.

 

When you say the ses light starts flashing when you turn the key to the on position. Does it flash once, pause, flash twice, and then repeat itself like 12,12,12? Have you done anything under the dash around the center console lately?

The Trickster!!!!!!!!!!!!!

 

OK rgarcia63,

According to my GM service manual in their diagnostic circuit check. Your flashing ses light when you turn the key on means that pin "B" of the ALDL is grounded somewhere between the ALDL and pin "A9" at the ECM. Hope this helps you some!!!!!!!!!!

The Trickster!!!!!!!!!!!!!

 

Trickster,

No the SES doesn't flash any codes as a matter of fact it won't stop flashing, like it's in the field service mode with KO/ER and first flashes a closed loop and then an open loop condition, but the engine isn't even running! That would mean the ECM is sensing zero ohms across the AB terminals and a pulse from the distributor amoung other things, hows that possible?, it may have loss prom data, but that should put it in limp home mode.

I'll try jumpering AB and see if it flashes any codes next Friday, I can only work on it on the weekends.

Can the ECM flash loop, or rich/lean conditions without AB jumpered? is this service mode even available for the 88 & 89s?


Not sure about the following information.

Manufacturer specific scan tool info
faculty.eicc.edu/dhanan/ep2/NOTES2.TRP

GM 1982-1993 - The PCM for fuel injected systems has several diagnostic modes:

1. 0 ohms or Field Service Mode - 0 ohms resistance between term. A & B of the ALDL.

Jumper or scan tool.

A. KOEO: Diagnostic Circuit Check

SES light flashes codes, all actuators on, IACV moves in and out or moves all the way in and stops.



B. KOER: Field Service Mode

1. SES light indicates open or closed loop; "rich" or "lean".

2 flashes per second, open loop;

1 flash per second closed loop.

Steady light "rich", no light "lean"



2. Timing is fixed at or above base.

DO NOT DRIVE THE VEHICLE IN THIS MODE!

 

Ok rgarcia63,

Jumpering pin "A" &"B" will not do any good. Pin "A" goes to a ground and pin "B" goes to pin "A9" of the ECM. When you jumper them, you form a circuit to ground for pin "B". What I am telling you is that somewhere between pin "B" and pin "A9" of the ECM, you already have a circuit to ground formed and that is your problem. If you would like, I can send you the page out of the GM service manual with that troubleshooting chart.

The Trickster!!!!!!!!!!