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88 CPE DV, 93 ELDO TOURING
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173 Posts
Discussion Starter #1
MY 93 ELDO N* 170,000, recently started a bizarre sequence. The PCM appears to do a power off restart sometimes when triggered by a voltage dip. This occurs randomly when I touch the brake pedal, turn on the headlights, turn on high beams, and starting. The symptom is the engine quits for an instant, the speedometer goes full clockwise, the tachometer goes full clockwise and the fuel gauge flips back and forth about once every second or 2 from about 3/4 to E, the AC comes on set at 75 deg in auto, the brake warning light blinks on and off sometimes, all of the computed outputs reset and there may be others I don't see. If its idling sometimes it stalls. The code is IO52 (reset memory or something like) and the snapshot shows all 0 s. The problem appears to be tied to the voltage dips from turning on things. It starts normally, and runs perfectly. The whole system acts perfectly normal until one of the triggers. There are two Ride level sensors disconnected that have failed, the two remaining appear to work properly. Touching the brake pedal while idling with lights on shows a noticeable light dim. There are degrees of severity like sometimes the brake touch will just cause a slight jump in the tach and speedo. The FSM has no close symptoms. Anybody have any Ideas?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,854 Posts
Re: Pcm gone wild?

Loose/corroded battery cable/terminal(s), 12 volt power wiring, grounds, other power sources. Every time you add an electrical load the system "droops" beyond low limits.

Running voltage between 14.2 and 14.8 in the DIC or measured at the battery terminals with a good VOM ?
 

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98 DeVille, 97 DeVille d'Elegance
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7,345 Posts
I'm with Sub... Bad/corroded electrical connection somwhere. Start at battery and main engine ground.
 

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Registered
88 CPE DV, 93 ELDO TOURING
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173 Posts
Discussion Starter #4
:)Thanks guys. Went to the positive terminal first, no outward sign of corrosion, but on dissassembly found a small, layer of corrosion between the spacer and body power lead. Cleaned er up, like new now. Thanks again.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
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69,854 Posts
Thanks for the comeback - Now, keep cleaning. Bet you'll find more nasties - every terminal/stud/connector on both battery cables and their body/fuse box connections.
 
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