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Discussion Starter · #1 ·
So I've been chasing electrical gremlins around the engine compartment trying to solve a no-start issue. During this process, I subscribe to "alldatadiy.com" ... can't recommend that enough ... it's been invaluable.

Anyways, there are two control pins on the starter relay. According to the pinpoint tests, one should have 12V in start. After much poking around, that's good (they also seem to specify the opposite control pin --- seems like an error).

The other pin should be "grounded" in start. It's not exactly. In run, it's about 40 ohms and that goes down to 33 ohms in start. I'm thinking this is not quite good enough to trip the relay.

Does that mean I need a new PCM? Partsource said something about needing to flash it before it would work?

What is the PCM doing here ... am I better to just wire up a "start" button? Or hardware that pin to ground? Does starting without a signal on this pin explain the puking of (what I now know was) transmission fluid? Last time I started it (by jumpering the relay) the transmission spit out about a quart of fluid.
 

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I would suspect a circuit or connector problem before I would suspect a bad PCM.

Alldata is almost as bad as Chiltons / Haynes as far as errors go. What did you use to verify 12 V at the relay pin? A DMM or a test light? Always use a test light to verify 12V on a power circuit. A DMM deaws so little current that even with high resistance in the circuit that the DMM will read 12 V..... the resistive voltage divider law in action.
 

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Discussion Starter · #3 ·
I suppose one reason I'm questioning this result is that I get a 40 ohm resistance in what should be the "off" state. Or is it? Is the PCM just preventing you from "starting" a running car?
 

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The PCM doesnt use an internal on/off relay to ground circuits for activators, it uses a transistor switch / pulldown or pull up resistor combination to switch outputs. Ohm meters can read weird things with solid state switches. The correct way to test this is tap into both pins of the relay coil. Be sure the hot side of the coil has 12 V with a test light. I THINK this should be hot with key in start or run, not just in start, as I seem to remember this relay is powered up via the VPWR circuit. Now, monitor the relay coil to PCM circuit with a DMM set to Volts. With key NOT in start, it should read 12 V. With key in start, it should read close to 0 Volts (maybe .7 V or so).

Have you checked the resistance of the circuit from the relay terminal to the PCM terminal? This should be around an ohm or so. If this circuit is 40 ohms, the circuit is bad. If that is the case, I would overlay the harness from the relay to the PCM with a new wire.
 

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i'm have a simular problem of the car not starting but I'm blowing the pcm fuse unless I unplug the big connection that sits right on top of the trans. now have to see which one of those little pins is the culprit although one of those little wires shouldnt have enough juice to blow a 30 amp fuse right?
 
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