Nicholas Evans

hey guys, i have a 2003 Honda civic dx auto. i just bought the car,i was driving it home and it went into limp mode wont go past 80. no power and wont shift right. when i get in the car now i can start it. engine revs up 1.5rpm then check engine light comes on rpms drop check engine light goes out and so on. dose this about 5-10 times. after that, rpm tack dies and heat gage. check engine light stays on. car will drive but i have to shift it from 2 to D3 and then it wont shift out of 3. when i first get into car the green key flashes at me also before starting. ive tried reading the codes, reader wont read them connection error. took it to a mechanic same thing they cant read the code.

car was a rebuild

ezone

Someone forgot to tighten the alternator bolts.....now it's ruined the PCM as a result.

Just a guess, but it's a great guess, it's a spectacular guess. A tremendous guess.

Nicholas Evans

PCM? The guy I got it from did mention he replaced the altternater, maybe your right . Is there a way I can test this PCM?

ezone

Only in a car that you know is good.

The telltale is the PCM can't talk to a scanner anymore, for me that's been the indicator it's too late to save it. You can try tightening the alternator mounting bolts and see if that solves the other problems, but I won't hold my breath.

A PCM will need programmed (for the immobilizer system and keys) before it will allow the engine to run.







Got one in the shop today....Complaint was just something about the transmission doesn't shift right, but we see all the warning lights are on, the key symbol was flashing, no scanner communication, etc. etc..

The top bolt for the alternator was backed out and has been run loose for so long that stuff has worn away and the alternator is sitting crooked. It's probably worn the big bolt into the letter Z and its hole in the bracket is probably a long oval shape now. PCM is junk, for sure.

I wonder how much money he saved by getting that timing belt done CHEAP at the corner garage?
The cost to fix the damage might be worth more than the whole car.

Nicholas Evans

Thanks for the reply I'll have to check the bolts on the altternater tomarroww sometime . The thing is the car stills runs and drives dosent have much power can't push the gas to much and won't go over 80.The key light dosent show up on till I shut the car off then the green key light flashes at me. What's the difference between the pcm and the ecm? Do they have the same syptoms? Or is more a guessing game?

ezone

That one is normal. Flashing that light while running is not normal.
The symptoms noticed in each case can vary a little too. Some people notice a bunch of clicking relays behind the glovebox, others don't notice it.

The car that rolled into our shop yesterday came from about 30 miles away, the only complaint was they thought the trans has problems because it doesn't shift right....totally ignoring several other glaring and obvious (obvious to us at least) issues right in front of the driver. (D light flashing, immobilizer light flashing, check engine light on, gauges whacky, low power, low rev limit, etc.) Scanner communication was nonexistent.

The gauges that went dead or inaccurate all operate using data on a network that comes from the PCM, so when the PCM gets corrupted you can "see" that result in the gauges activity. (I think the fuel gauge is the only one that does not run solely on data from the PCM, so it could have still read accurately)


Leaving the alternator bolts loose is such a common oversight that Honda issued information about it back in 2004.

The poor or lost grounding of the alternator housing leads to the inability to control charging voltage accurately, leading to excessively high charging voltage, and sensitive electronics can become damaged when the voltage gets too high (somewhere above 17v damage can occur).


You can search this forum for 'loose alternator bolts' and probably find 50 threads on it. (Correction, 207 threads LOL)

Both refer to the same computer, and the acronyms are used sort of interchangeably in the field.
Technically and according to OBDII standard nomenclature, a PCM (Powertrain Control Module) operates both engine and transmission (usually automatic trans) from within the same control unit, and an ECM (Engine Control Module) operates just the engine on manual trans equipped cars and cars that use a separate control unit for the transmission.