Rep Power: 0

I have a 2002 and 2001 honda civic coupe EX with this problem and i searched everywhere to figure out the problem but i cant find if someone actually fixed it.

the problem is my 02 honda run perfectly fine when its COLD but i can drive about 30min and then my car lost alot of horse power it runs really rough and sputters and backfires and also i cant pass 3000 RPM because it rev limits for some reason, i can hardly go 20mph. if the car sits and cools off it starts perfectly fine and has full horse power as if nothing happened. as soon as it hits running temp then it all happens again.

i also would like to add that i read the ECM could be a problem and needs to be replaced but i also noticed they said that when the car is in "limp mode" but my car isnt in that mode. my 01 honda is in limp mode but my 02 honda is having the same issues my 01 honda had for a year BEFORE it went into limp mode after the alternator went out and shorted it out. i noticed the relays click every 10 secs and my car hickups on my 01 honda.

My 02 honda civic is what im trying to fix and i would like to know what is causing the car to lose power when warm. i herd alot of suggestions but alot of them didnt help or wasnt comfirmed that it worked so im just trying to find out myself what to do.

thank u for taking the time to read this and helping me out.

 
Rep Power: 519

GOT CODES? Or does a scanner no longer communicate with the PCM when it acts up?


Someone forgot to tighten all of the alternator mounting bolts? Stop driving. Check it now before the PCM is completely ruined.


Did the same person forget to tighten the alternator on both cars?

 
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theres nothing showing up on the scanner for codes, it doesnt even read the car, and i just put in a new alternator and i checked the bolts all are tight and its still has the same problems like loss of power after driving for 30min. it no longer hickups though.

 
Rep Power: 0

i forgot to add that i read something about my wire harness could be grounding out when it touches somewhere, but could it be touching at a certain temp? because it runs fine when its cold.

 
Rep Power: 519

If it can communicate with a scanner while the engine runs ok or is cold, it might still be saved if you fix the root cause.

If it never ever communicates with a scanner, the PCM is ruined.

The question now is "what caused it?"
High voltage causes it. Running the alt with loose mount bolts or a bad or weak ground causes runaway voltage....and it ruins the PCM.

The most common reason is because someone forgot to tighten the alternator mounting bolts during any work involving the alternator (timing belt job).
It's so damn common someone forgets to tighten it, Honda issued a service bulletin specifically addressing it.

If it was never ever left loose, some other stuff to look for is bad and/or corroded grounds of the block/trans/body/battery, and corrosion causing poor electrical grounding of the alternator and it's mounting bracket.

 
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I was wondering if the ground did have something to do with it because of the sudden loss of power when its warm, so i was thinking an electrical problem was the case. the ground on the engine is in a funny spot(from the engine to the bracket behind the hood latch) so i was wondering if the engine warms up and the temp of the metal changes the ground on the engine causing it to suddenly stop working. is there an alternative spot to wire this ground? sorry if this sounds dumb but im still learning and im just throwing ideas out there. im really trying to isolate the problem for me and also anyone on this forum because i am so stumped on it.

 
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The 02 civic PCM works while cold but still no codes. I was also wondering if there is an alternate place i could place the engine ground wire because i was thinking the engine warms up and messes with the connection to it. its connected to the bracket behind the hood latch so i was wondering if that's a good ground or not. i didn't place it there so i'm not sure.

The 02 civic doesn't hiccup at all and the alternator is working good also wasn't touched or changed. The car warms up and i lose power down to a crawl.this is the car i want to fix and change the ground.

The 01 civic does hiccup and i believe the PCM is gone because it doesn't read at all even if its cold or hot. the alternator was changed because the belt came off while i was driving and fried the PCM. so i gave up on this car and i'm just using it for partsBUT this car had the same issues as i'm having now with the 02 Civic soo whats going on, it seems common or i just have bad luck.

 
Rep Power: 519

No codes, or no communication? HUGE difference.
Does it lose communication after it warms up?




That's the stock location for the braided cable. (The main PCM grounds are bolted on the water neck right next to the braided cable, clean that up too)

The neg battery cable is the other ground.....follow that from battery to body then to transmission.


Take apart all connections and use a wire brush til you get clean shiny metal exposed for good contact on all mating surfaces (and the bolts). You could also do voltage drop checks (loaded) to make sure it doesn't have an internal resistance problem. Also do a voltage drop check from the alt housing to battery neg post, because this is where most PCM killing problems originate.

I'm focused on the most common issue that results in "no communication" and a ruined PCM stuck in limp mode.
When this happens, most people report their gauges go whacky at the same time...Do yours?

Maybe the two cars have similar symptoms ("it won't go!") but completely different problems and causes. Several things could cause severe power loss, but not many can cause loss of communication with a scanner.

 
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Okay i got some codes and they are P0122 and P0141

P0122 also had this in the scanner
Throttle/pedal A
Position sensor A
Circuit low imput

P0141 had this
oxygen sensor
heater circuit bank
1 sensor 2

any ideas what these mean?

Also i checked the alternator and you was right the bolt for the alternator was falling out so i'm going to replace the alternator an fix the belt tension

 
Rep Power: 519

The alternator is probably fine if you get the bolts tight.
Then after the bolts are tight you can see if the pcm will survive.

Does the scanner display live data?
Got freeze frame data?
Check tps value in data, see if it's reasonable.
Erase code, see how long before it resets

 
Rep Power: 0

ok so i did what u said and tightened back up the alternator and then i reset the codes and they instantly came back. Should i proceed and change the 02 sensor and replace the tps too? and is those sensors the reason my car losses power when its hot?

i didn't check the tps value and the scanner does not display live data or have freeze frame.

everything seems to be the same but i also wanted to add that there's the abs, srs, engine and battery lights on. it was like this when i bought the car. the only light that wasnt there before was the battery light and that came on recently so im not sure why any of those came on. and is there a way to fix the lights and fix the parts so they arnt on?

 
Rep Power: 519

well, it may be tough if you can't get fault codes and data from those other systems.

So you tightened the alternator bolts....have you driven it around a while , long enough to see if the scanner still loses communication after it's been driven?


Got a DVOM?


Assuming the scanner doesn't lose communication now.....let's first see about the battery warning light.
Turn the key on, do not start the engine. Open the hood and unplug the 4 wire connector from the alternator. See if the battery warning light goes out.