Can anybody give me some hints on a good way to probe the ECM (computer) connector on my '94 4x4 Pickup with the 3VZE engine? My manual says to perform all measurements with the connectors connected, but there doesn't appear to be enough room to get a probe touching the connections even with the ECM sitting on the floor. Is this done with a very thin probe, or something else?

I'm checking the computer since my engine shut down the other day while I was driving and now it will turn over but not start. It gave no warning - just shut down while I was cruising.

I added 2 gallons of gas first (just in case) and then I verified that the ignitor is working (spark test) and I used a timing light with an inductive pickup to check that I get a spark to each cylinder. The EFI and circuit opening relays check out OK per the tests in the manual and I can hear the fuel pump running and feel some pressure in the hose when I force it on (B+ to FP on the diagnostic connector). I can also sometimes smell fuel after cranking the engine but I don't have the gauge and adapter to check fuel pressure. I'm up to the point where I need to check the volume air flow meter circuit at the ECM. I checked the meter by itself and it seemed OK although the resistance between E2 and VS was a little lower than 200 ohms with the plate closed.

Anyway, I'm working my way down the list, but any ideas would be appreciated. I'm getting close to the point where I may have to tow it to Toyota.

Timing belt?

Regular old straight pins from the sewing box makes for an excellent probe when working in tight places!!

Guess the plugs wouldn't spark if it was the timing belt....duh

Have you already checked ground wires, vaccuum hoses, and basic connectors etc., under the hood? Kickpanel, behind glove box fuses, although I cannot remember if there is any engine control stuff there. What you are doing seems pretty nitty gritty, and if you have not tried that yet, I would start there. Otherwise, I have not had to do that one yet and do not have any tricks of my own. Curious however and would definately like to know the outcome. GoodLuck

Thanks for the replies. I'll have to borrow some needles from my Wife!

As for the other things - Yup, the first things I checked were ground wires, vacuum hoses, connectors and anything else that looked like it might have fallen off. I only found 2 ground wires (one to the intake manifold connecting to the firewall, and one from the LH head to the fender), but both are good. I also tried to pull the codes, but the ECM thinks everything is OK. That's when I had to open the manual and start walking through the list of likely problems.

I'll post when I find the problem or (more likely) when I have more questions!

is the 3vze a interferece motor? if it is and the timing belt broke you SOL

Regarding timing belts - I'm 99% sure that the distributor is running off of a gear on the left hand camshaft. If the belt was broken, the distributor wouldn't turn.

Also, I did a little research and found http://www.gates.com which has a timing belt guide that shows interference engines. The 3VZE is not.

Anyway, tonight I verified that the air sensor was OK and the ECM was seeing good signals. It was interesting to hear the fuel pump come on when the ignition switch was ON and the air volume sensor door flap was pushed in a little bit by hand. That seems like a quick and easy way to check that the EFI relay, Circuit opening relay, fuses, air sensor and fuel pump are all working if you're ever in a similar situation. Between that test and a spark test from the igniter, it seems like you can pretty quickly eliminate a lot of possible problems.

Then I decided to pull out a plug and double check that I'm really getting a spark (perhaps a timing light isn't a good way to check this). When I pulled off the first wire (carefully - I know the right way to do it!) it broke off from the plug connector with no real force. These are "Original Engine Management" wires that I got from BAP. I'll replace them with true OEM parts and try again.

Sounds good, and yes the distributor would not turn if the timing belt was broken. There is another ground wire. It starts off of the harness down by where the a/c compressor is. It then connects to the block or head I can not remember right now, pretty sure to the head, anyways, this is another thing to check off your list if the new wires don't work.

I took a 10 GA stranded wire, stripped it, and took 2 strands off that wire, twist them.. Stick 'em in the ecu connector.. Probe the strands.
If they're not firm enough, solder them together.