Check engine light

[dixiechevy01]

Check engine will not come on in my 87 k5 blazer its got the 350tbi. It doesn't come on when you turn the key on like it should. I just replaced the bulb in it. I should've checked it for power while I had it apart but I didn't think about it. Are there any common problems with these I should check first before I go tearing into a wiring problem

 

[crazedyak]

NO Service Engine Soon (SES) LIGHT

---DOES THE ENGINE START-- YES

1) Ignition Off
2) Disconnect ECM connectors
3) Ignition On
4) Probe circuit 419 (brown/white) wire with test light to ground
5) Does the SES light come on?

If Yes
1) Faulty ECM connection or faulty ECM

If No
1) check fuse
2) faulty SES bulb
3) Open in circuit 419
4) Circuit 419 shorted to voltage
5) Open Ignition feed to bulb



DOES THE ENGINE START -- NO

--- Is the continuous battery fuse and ECM fuse OK?

NO
1) Locate and correct Short to Ground in circuit that had a blown fuse.

--- Is the continuous battery fuse and ECM fuse OK?

YES
1) Ignition Off
2) Disconnect ECM connectors
3) Ignition On
4) Probe Circuit 340 (orange) and circuit 439 (pink/black) with test light to ground
5) Is the light "On" on both circuits?

YES
1) Faulty ECM grounds or faulty ECM

NO
1) Repair open in Circuit that did not light the test light.


Do that check to clear your No SES light


This is a 87 350 Drawing

 

[dixiechevy01]

Thanks for the info. Looks pretty straight forward. Is the ECM located on top of the intake?

 

[crazedyak]

No, the ECM is behind and above the glove box. Take the glove box off, and look above it for a silver box with two bundles of wire going into it. That would be the ECM.

You are going to have to trace wires unfortunately to find the issue., The guide I posted above is a great reference to start. At least you know the colors of the wires you need to look out for.