Jeff Bouchard

I have a 95 4Runner with the V6 3VZE engine in it. I just rebuilt the top end after the head gasket had failed. I bought the truck with a blown head gasket so it wasn't running when I bought it and I didn't realize that the check engine light was not coming on. I went to to smog it and they wouldn't do a smog because the check engine light will not come on in the "on" position. I pulled the instrument cluster and someone had jumpered the check engine light over to another bulb, I think to get it to turn on at start up, and then stay off. I pulled the jumper, replaced the bulb, and I still cannot get the check engine light to come on. The "brake" light also does not come on, but the "ECT Power" in the same set of lights powered by the same electrical connector works fine. Anyone have any ideas as to why my CEL won't come on and what to look for? Thinking I need to start running continuity checks to the ECU but not a electrical guru so assuming it will take a little effort. Any help is appreciated!!

scope103

First, make your post once. Don't put it in multiple places (if you want useful responses).

It sure looks like continuity checks are in your future. These (which are nominally for a '93) should help:
http://web.archive.org/web/201003261...e/102engin.pdf
http://web.archive.org/web/201102052.../6combinat.pdf

The wire you are looking for is "W," which in my EWD is Violet (no stripe). It should be A9 on the combination meter, and A5 on the ECM. It is Active Low, which means it pulls to ground with key-on, engine-off. Once the engine starts (and you have no codes) it should go to high impedance. W also appears on the diagnostic connector, so I would start there to confirm that the connection to the ECM is good. If you get the right voltages at the diagnostic connector, you can be pretty sure the problem is in the Combination Meter.

Jeff Bouchard

So I checked voltage at the "W" on my diagnostic connector and no voltage in the "on" position. Also no voltage out of the ECU when in the "on" position, engine off. Does this mean I have a bad ECU? The whole rest of the truck runs great, no problems.

scope103

Probably not.

"Active Low." What you need to do is measure voltage FROM 12v to W. When W pulls to ground, your meter shows 12v. When it goes to high impedance state, well, who knows what it will read from that super-sensitive digital multimeter. Probably close to zero. This is actually easier to do with an LED test light (what? You don't have one? That's because no one (SFAIK) makes one; the polarity issue is too confusing.)

In any event, the W line should pull to ground (0v to ground) with key-on, engine-off.

Jeff Bouchard

So I figured out what was wrong, the circuit board ribbon had a tear/cut in it. Now the check engine light comes on, and stays on. I am not new to checking trouble codes, but now I can't get the light to flash. It doesn't do the flash every half second either. It just stays on. Actually, when I connect TE1 to E1 terminals, the overdrive light starts flashing. Any idea why this would happen? Someone messed with the wiring or? Not sure what's going on now, just want to check trouble codes and fix this thing!! Any information helps! Thanks!