"Service Engine" light on TBI

[carpeonnel]

TBI question: got an '89 Blazer in which the service light keeps coming on periodically. It's been doing this for about 2 years now and I can't figure it out. Now, my Blazer has always idled high in park (right around 1200) but now when the light comes on it'll idle down to about 700 or so in park. It won't idle down all the time when the light comes on, but most of the time it will. But the strange thing is, when the light's on it runs better. I replaced the O2 sensor thinking that might be it, but no luck. Any ideas out there?

 

[romeolimagolf]

Try pulling a trouble code. It will tell you where to start. You can do it without a scanner. Here's how:


1. With power off, connect a jumper wire across pins A and B. ( a paperclip works well too) That should be the two upper right pins as you look at the plug.

2. Turn the ignition to ON but DO NOT start the vehicle.

3. The Service Engine Soon (SES) light should flash code 12 (1 flash, pause, 2 quick flashes)

4. After a longer pause, code 12 should repeat two more times.

5. If there are any codes stored in the ECM they will follow Code 12.

6. If no other codes have been stored then Code 12 will continue to repeat until the jumper is disconnected.


This procedure only works on ODBI (pre 1996) vehicles.

 

[carpeonnel]

If it displays another code where can I find out what that code means

 

[romeolimagolf]

If it displays another code where can I find out what that code means

http://www.gmtuners.com/OBD1_DTC.htm


And I want to stress that trouble codes DO NOT tell you if any parts are bad. For example, just because you get a code for a Throttle Position sensor, it DOES NOT necessarily mean the Throttle Position sensor is bad. All it is telling you is there is a problem in that circuit.

 

[shaun89]

mines an 89 and it does the samething, it was code 44 and it said high voltage at the O2 censor...if i remember correctly, so i replaced it, then i reset my computer (pulled neg. off battery for a while) and it came on again, it threw code 42 which is low voltage to the O2 censor....then i gave up because im going carb with my new engine...im not sure how my story might help you, but i kept you busy for a minute maybe