Dreaded trans. Failsafe prog.

[Oldmactech]

Good idea, I have a cheap one, always glitchy. Will retry.

I’m not sure visual inspection will get me where I need to go as these O2 wires are wrapped in a rubberized shroud but one shroud definitely has been partially removed either heat or critter damaged.


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[Oldmactech]

Well, I guess I’m going to have to tear into the O2 sensor wiring and look for a short. Appears from continuity test that the Dow streams are not getting current but oddly when I hook my OBd 2 scanner up they transmit data but not the upstream. And both are not functioning.

I really don’t won’t to tear into the harness past the rear of the engine as it seems damn near possible I could get a wire back where it needs to should I even find a short.

Studying the Bentley diagram shows that red/ws feeds power to the O2 Heater all4 wires. With a brown, yellow and black wiring going to the DME.
I’m confused by the block diagram, I assume the .5 is the wire size?
The numbers next to the wires, are those PIN numbers? I also see what looks like a fuse 5v(15) inside a6000 DME? I would assume if there is a DME fuse inside there would only be one and the car would be dead.

Likely I’m over complicating this and it’s something simple right in front of me…..

On the verge of taking to an Indy but still being stubborn (and trying to learn something in the process)


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[Oldmactech]

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[wpoll]

That's not a fuse symbol on the DME block - it's a resistor. The resistor and transistor symbols simply indicate an actively controlled input or output on the DME module, nothing more.

In this case the O2 sensor has +5v (voltage) on one side of the sensor element, via a current limiting resistor (most likely).

[Oldmactech]

Got it, thanks.


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[Oldmactech]

Originally Posted by Oldmactech

Got it, thanks.


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Ok so my helpful neighbor brought over one of those power probe knockoffs to try to isolate the short. My question is if I bypass the fuse that blows and inject 12v into the Red/white stripe wire will I a) damage anything? B) learn anything?

The probe has a circuit breaker so I’m slightly comfortable but not completely.
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[andrewwynn]

If it has ckt breaker nope won't learn.

Almost certainly just one of the six wire runs is shorted. It literally takes 20 seconds to crimp them back together, cut the crimp off, measure each power to ground and find the short then trace the shorted wire to find the fault.

Didn't you say when everything unplugged still blew the fuse?

Actually, that tester might work better than DMM for testing the short however. Once the lines are isolated. However with the O₂ unplugged the lines will read open ckt unless fault exists.

A yellow butt splice should work to connect everything back up. Blue maybe and put half in each side (electrons can make a u-turn it's not like plumbing where corners slow it down)

[Oldmactech]

Ok, thanks. I pretty daunted by tearing into the wiring bundle. I don’t mind cutting and butt splicing near the fuse connection but I guess it makes more sense to peel the heatshrink off the suspect O2 wires that I can actually see before trying to find a short in a packed in bundle that would be nearly impossible for me to fix without taking half the firewall apart.

Also, not sure your last paragraph, unpack that for me please?
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[andrewwynn]

If I remember correctly the crimp is an end splice with all the wires going into one side. Those are more rare; it is easier to get butt splices and you can split up half of the wires in each side. My point is you can use either.

[Corellian Corvette]

If you have a Power Probe, you can feed power to each line on the O2 sensor circuit. You have the TCM removed, and the 02 sensors removed then no reason not to feed power to each wire and see which one trips the breaker.

Or you could simply get a test light and see which wire provides the ground to turn the light on?