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Persistent, intermittent, mysterious, and worsening electrical troubles!

I’ve got an 89 plymouth colt, ~100K miles. for last two years, an intermittent electrical problem has gotten worse and has eluded my good mechanic on several visits to his shop. for a long time it would manifest by periodically stalling out the engine while running, which would be accompanied by a clicking noise beneath the dash (master relay?). After a new relay was installed, then after several attempts to find a bad ground and clean them up, issue still resurfaces, and now has gotten worse (or maybe it’s new and different?). now the CEL light comes on and car goes into limp home mode. trouble codes include those for air flow sensor, intake air temp sensor, coolant temp sensor, idle speed motor control sensor, and baro. pressure sensor. car runs in limp home mode now, perhaps, 60% of time, and absolutely fine the other 40%. could all of those sensors really have gone suddenly bad? or do I have a voltage problem? one more potential clue: when I turn on my headlights at night while car is running, the master relay clicks a few times (but the car recovers). THANKS! gary in the carolinas

to be specific, the trouble codes I get are as follows: 12, 13, 15, 21, 25

My 86 Aires Had All The Same Symptoms. It Turned Out That The Problem Was With The License Plate! It Was On The Wrong Car!

That’s when I decided it was the end of the line for my old buddy. Bolting a different car (as in a little newer) to that plate fixed everything and I had no more problems or trouble codes.

I forget what that thing is called that’s an ECM and air flow box all in one, but I figured that’s what was wrong with mine. I swapped one with my other Aires and it did’nt fix it, just before I had it “put down”.

On a more serious note, have you checked Allpar for help? Here’s a link: http://www.allpar.com/

CSA

[b]Gary, I Clicked On “Repairs” At Allpar And Here’s One Thing That Looks Like It Could Go With Multiple Trouble Codes And Aging Cars.[/b]

link:
http://www.allpar.com/fix/driveability.html

CSA

thanks, CSA - and ha! I do realize the sense in your sarcasm. (but honestly, when this thing works, it’s really great, AND gets about 40 mpg!)

in any case, I did read over the link you provided and have done those steps atleast on a cursory level. I’ve also had a shop mechanic spend quite a bit of time over a few visits at which time he cleaned up and re-secured some grounds. Nevertheless, the problem keeps coming back, so I"m still looking for possibilities. (like… could a faulty alternator be producing an output voltage too low to properly ‘run’ all those sensors while at the same time high enough to keep the battery charged???)

thank you for your response - and cheers

Gary, What About The Connection Right At The ECM?

I had multiple intermittent codes from a BCM (body) on my Caravan. The Module/connections were getting old.

The ECM (engine) on my Aries(plural? I had 3) were located in the “kick panel” just ahead of the passenger’s side door. I’m not sure if your’s is there. What about cleaning the connection?

CSA

yup - my ecm is there too. I’ve pulled the thing out to have a look. all harnesses going in to all connectors on the ecm itself look surprisingly clean. in fact, the ecm appears to be a ‘new’ one for the car (info about being a certified remanufacture part, etc. I’ve had car for just over 2 years so who knows what it’s gone through before). I even opened the ecm up to look inside, and, again, the circuit board in there look really good (save one little…‘transistor’ (?) that had a little corrosion on it)