97 Expedition stalling, then theft light blinking

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CARO'S98EB

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If you have no link [no communication ] with the pcm when this happens I would guess that it could be either the pcm relay or the pcm. if the pcm relay is bad no power will get to the pcm causing it to not communicate. since the relay is much easier and cheaper I would start there. It is a standard full size Bosch style relay you can get one at any parts store.
 
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PO'dexpd'nowner

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Relays are cheap whether they are old school or completely electronic and you can swap these out yourself.

For less then the cost of the repairs you are mentioning, you could swap ALL of the relays and fuses.

The PCM relay is $226....definitely not cheap. Any way to test it before replacing? Keep in ind it's intermittent
 

Captain Morgan

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Let's move these 2 posts back to your thread for continuity, it gets confusing where to find questions and answers hopping between other persons threads . . maybe a kind mod or admin will do the move some time today :D


Please restate which year and package is your vehicle, thx!
 
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PO'dexpd'nowner

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97 Exp'n XLT package I think. Searched ebay and found nothing. Do you think it would worth it to buy a used PCM relay for $50 or so from a junkyard...maybe less?
 
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PO'dexpd'nowner

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I found a guy parting out a 97 Exp'd so I'm gonna try to get a PCM relay from him. It was $226 at Autozone. I offered him $20 and I think he's going to take it. Where is it located anyway? The autozone pic shown here http://www.autozone.com/autozone/pa...9cj87?filterByKeyWord=relay&fromString=search makes it look like it will not fit in a fuse box. When you said relay, I was thinking of a little black square less than 2" long.

For some reason, after reading Caro's response, I don' think I'm looking at the same/right thing.
 
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Captain Morgan

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I thought you already had the PCM swapped out?

The PCM is not a standard relay . . . it has high current rectifiers in it and is a solid state device. It's a smart switch of sorts. Thus the price.

Nevertheless, it has connections and switches current and the clean connection principle still applies.

If you've already swapped it out once, I honestly wouldn't bother with it again other than checking the connections to see if they are clean etc.


Then again, if you can get a good PCM to have on hand, $20 isnt a bad investment. Hell buy ALL the relays of that parts vehicle and have them as spares.
 
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PO'dexpd'nowner

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I thought you already had the PCM swapped out?

The PCM is not a standard relay . . . it has high current rectifiers in it and is a solid state device. It's a smart switch of sorts. Thus the price.

Nevertheless, it has connections and switches current and the clean connection principle still applies.

If you've already swapped it out once, I honestly wouldn't bother with it again other than checking the connections to see if they are clean etc.


Then again, if you can get a good PCM to have on hand, $20 isnt a bad investment. Hell buy ALL the relays of that parts vehicle and have them as spares.

I did get a new used PCM for it off ebay.....with same exact results...thus the reason I don't think it's the pcm but something else, like the relay. The $20 would be just for the pcm relay, not a new pcm...unless I'm all mixed up on these parts.
 

Captain Morgan

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http://wiki.answers.com/Q/What_is_a_PCM_Relay

http://wiki.answers.com/Q/What_does_a_PCM_power_relay_control

http://wiki.answers.com/Q/Is_a_fuel_pump_relay_and_a_PCM_relay_the_same

http://wiki.answers.com/Q/What_does_pcm_power_relay_mean_on_ford_explorer_1996

"The PMC stands for Power train Control Module. it controls various sensors and relays throughout the engine, by sending voltage singles according to what the sensors receive."


Like I said, smart relay. If it's screwed the whole rig is screwed, but if it get's tons of bogus information from other bad sensors, unexpected intermittent connections and or shorts, it will send the rest of the system in to a frenzy.

The PCM Relay must have solid connections for power and solid communication paths or the rig will act horky. All you can do is check and clean these connections and clean\replace the other sensors, the PCM relay isnt meant to be opened up and have dust blown out if it etc.

ex:

"The PCM control the fuel pump relay on this vehicle. In addition, the fuel pump relay gets powered up from the red wire from the PCM power relay.

Anything preventing the PCM from waking up or anything preventing the PCM power relay from working will prevent the fuel pump relay from activating and of course will keep the fuel pump from getting power."
 

hovocop

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my 98 is worth around $3500............ any repair with risk of $1000 or more would mean a death sentence ........... thats all I meant with money pit................ I have put in $700 in repairs in just these 3 months..................
 

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