jjrbus

93 Toyota cab and chassis, V6 auto, 98K miles.

My check engine light is not working. When turing key on all lights come on except the CEL.

I pulled the cluster and checked the bulb, it is good. I did a continuity check on the wire from the ECM to the bulb and have continuity.

I grounded the lavender (CEL) wire at the ECM which is suppose to test the ECM light but nothing, no light.

Any suggestions? Jim

scope103

I responded here https://www.yotatech.com/forums/f116.../#post52321096 before I read this post. If you have continuity on the Violet wire, grounding at the ECM has to ground at the CEL. So now check the other side of the CEL (Black-Orange) for 12v. Black-orange continues back to pin 9 of the Integration Relay.

jjrbus

Thanks for the response, greatly appreciated.

I have 12V at the black orange. Jim

jjrbus

Went and read other post. I am not sure on this, I pulled the plug at ECM and checked the W plug for continuity to ground with continuity tester and shows no continuity.

I suspect that is not what you meant?

Then had a thought, I am unplugged from the ECM, 12V is supplied to the bulb from the integration relay and the ECM supplies ground. So I grounded W wire turned on ignition and light came on.

Then I though I should have asked before I tried this, no smoke or sparks or anything.
Jim

scope103

Correct. The violet (ECM A-5) wire is grounded by the ECM to turn on the CEL. In normal operation, the W pin of the diagnostic connector matches the ECM pin; since it is "pulled up" by the 12v through the (unlit) CEL, you can "read" the codes at the W pin by watching the voltage swing.

If your ECM is not pulling A-5 to ground with key-on, you may actually have a bad ECM. But as I said; ECMs are very tough, and the problem could lie elsewhere. Like all the times you've pulled the connector on and off might have lead to a bad connection.