NEED HELP REP and No Start

TobyU

Original poster
Member
Oct 31, 2019
34
SW Ohio
Hello all,
I am also fighting an intermittent no start on an 04 4.2.
I have had a constant fan code forever but it has been running fine. I get a P0651 I think it is loss or 5v B signal and cam code sometimes when when it runs fine.
When it will not runs it always is only when it is cold after sitting all night and it starts and dies in 20-30 seconds .
Then the Reduced engine power light stays on when key is turned on and does not go out in 2 seconds with rest of lights.
If I can get the REP light to go off---it starts and runs fine for rest of day with lots of re-starts.
It seems possessed.
I've been looking at the PCM three plug pin outs but haven't dug into them yet.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Hello all,
I am also fighting an intermittent no start on an 04 4.2.
I have had a constant fan code forever but it has been running fine. I get a P0651 I think it is loss or 5v B signal and cam code sometimes when when it runs fine.
When it will not runs it always is only when it is cold after sitting all night and it starts and dies in 20-30 seconds .
Then the Reduced engine power light stays on when key is turned on and does not go out in 2 seconds with rest of lights.
If I can get the REP light to go off---it starts and runs fine for rest of day with lots of re-starts.
It seems possessed.
I've been looking at the PCM three plug pin outs but haven't dug into them yet.

Have a read of my post #3. The fact that you have a fan code as well as issues with the 5V reference and REP does point to the fan clutch causing this.
 
Last edited:

TobyU

Original poster
Member
Oct 31, 2019
34
SW Ohio
Have another read of my post #3 above. The fact that you have a fan code as well as issues with the 5V reference and REP does point to the fan clutch causing this.
Certainly sounds like a possibility but it's never had any effect to unplug the fan clutch. I guess it could be in the pigtail connector leading to the fan clutch itself and not in the fan clutch's where two wires could be touching and shorting out the reference signal but I've never found it to make any difference messing with the wire going to the fan clutch. The other poster was able to get theirs to start after unplugging the clutch. Mine still has the reduced engine power light on and just cranks.
I'm not certain how the system works but of the three or four things on that reference signal circuit which I think mine is the B signal, if a vehicle is working properly and you unplug one of the sensors I don't believe it makes the reduced engine power light come on.
So if I assume a sensor is shorting mine out, unplugging that sensor's wire when mine is in the no-start condition should unshort things out and make the reduced engine power light go out but I haven't been able to test it this way.
 

TobyU

Original poster
Member
Oct 31, 2019
34
SW Ohio
Download the manuals and check the schematics for the 5V reference. Could be a short or break somewhere that affecting it.

And unplugging a sensor might not help if it's something like the pedal sensor or the throttle body, both of which are on the same 5V reference.

Thanks for the suggestion.
Here is the exact history as best I can recall:

Truck has been running perfectly for a couple of years since we got it.
Now about 3-4 times when we first got it if you gave it a lot of gas taking off fast it would go into reduced power mode and was fine on restart.
I never even ran the codes. It never did it to me as I take off easily. My wife got used to not hammering it and it was fine for 2 years.
I knew it was probably the tps on throttle body.
Out of the blue one day it started fine and then after about 20 to 35 seconds died. The reduced engine power light ( REP) came on as it died and stayed on.
It would not restart.
When turning key off and back on all the dash light would come on for the normal test etc and the y would go out but the REP light would stay on. It never did this before.
Tried a bunch of times to restart and no luck.
Was pushing it back to driveway and hit the key and it started and was fine all day.
The next day, same thing. Ran 30 seconds and died.
I put it in N and rolled it about 5 feet and it started up. I did this at least 3 days and it was fine for rest of day.
Then that stopped.

I went to pick and pay lot and got a fairly clean throttle body and replaced it. Same thing the next day.
Then I got another pedal...same thing.
I was getting all the signal a and b mismatch pedal codes etc and the loss of 5v reference and a cam sensor code.

I bought a new cheap amazon throttle body and put it on and did reset calibration procedure and it started right up and ran fine.
Did pop a cam code multiple times and I swapped it out for a used one and no change it was fine for a few days.
Then it would not crank one day. Went out and dash lights were dim but goo battery.
Has son sit in it and AS SOON as it touche the fuses inside the bod under hood the dash lights brightened. AHHH Happy now I'm getting somewhere.
One of the ing or pcm fuses was loose from having someone use one of those stereo taps and bent it out too wide.
I fixed that and it has been fine for about 3-4 MONTHS!

Yesterday I started it and in 30 seconds it died and REP light popped on and no start with light staying on just like originally. I pulled the fused and no change until I got to the yellow 20 amp pcm B I think by the fuel pump micro relay. I pulled the fuse and relay and when I put them back in the REP light was off with key on and it started and ran fine the rest of day.
I cleaned off fuse terms one last time with my shirt tail and hoped for the best.

Today, 20 seconds and died.
Pulled relay and fuse and on the 2nd time pulling them and putting back in it started!!!
I'm at a loss now.
I don't think it's a lose connection at lest not at the fuse and the FP relay wouldn't make the REP light come on.

It only messes up 20 secs after cold multi hour sitting start.

I did smack the top of ecm under hood with palm of my hand but don't think that did it. I pushed on the 3 connectors and wiggled and looked at wires and all look ok.
I think I might pull the 3 big connectors and reseat them but I am at a loss.
----------------------------------------

So both days I pulled the same fuse and fuel pump relay (not because the FP relay could have anything to so with it but because it make the fuse easier to pull.
2nd day still died. After pulling again and restart I swapped the two solid state electronic relays and it has been fine for 2 days. ???????
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I've moved your posts and created a new thread as your issue may not be same as in the other thread.

Sounds more like you have an issue with the fuse box or wiring. You might have to replace it. Pull it and see if something is going on under. You could pick another one up at the pick-n-pull.

If you have a simple code scanner, try to get the codes when it happens. We need to get those.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Yes it is.

So what did you do? Enquiring minds want to know!
 
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TobyU

Original poster
Member
Oct 31, 2019
34
SW Ohio
I haven't done anything since my last post. I pulled out the PCM B fuse just and wiped it off again but I did that the day before and it still didn't start the next day. The one next to fuel pump relay which I pulled out also. The only different thing I did that day will swap the two solid state electronic relays. The one for the fan and HDM which is something for the headlights.
Everything's thing still works the same it's just been starting out every morning. The headlights have never worked right.
They come on automatically on low beam or maybe it's just the drls and we leave it that way. They are on anytime the vehicle is started but the dash lights and tail lights come on at night... but the switch on the dash does absolutely nothing. You can't turn them off.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
That is normal operation for the headlights. The relays for the fan and headlights are the same.

Maybe the PCM just needed a reset. Hope it works out.
 

TobyU

Original poster
Member
Oct 31, 2019
34
SW Ohio
I thought that you should be able to turn the headlights on manually with the switch if you wanted to. Or hold it in the spring loaded position to change some setting or to turn them off when they're on at night but my switch seems to have no effect whatsoever.
Of course, it shouldn't have anything to do with the vehicle starting, not starting, or starting and then dying in 20 seconds but it just makes no sense. The vehicle just went on a four hour trip and has been starting and running fine every day.
I will note that the battery is getting weak and old and there's not much capacity left. If you go out and start it right up it's fine but if you were to turn the key to the on position and leave the headlights on for two or three minutes there's no way it would start. It only has enough off to turn the engine over about seven or eight times before it's exhausted his capacity.
I don't think this would affect my situation though. It always starts right up the first time each day it's just that in about 20 seconds turns off and the reduced engine power light lights up. I don't see how a weak battery could have anything to do with that but who knows with weird electrical demons.
It's just kind of weird. It has been fine for almost a year since we bought it and then everything messed up and I went through a used throttle body and then a brand new throttle body and a used gas pedal and then I found a loose connection on the one ECM fuse and it's been five for three or four months. Then out of the blue it died one day after I started it. Then it did the same the next day. And then after I swapped those two relays it hasn't died since.
 

Blckshdw

Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
I thought that you should be able to turn the headlights on manually with the switch if you wanted to. Or hold it in the spring loaded position to change some setting or to turn them off when they're on at night but my switch seems to have no effect whatsoever.

You should be able to turn off the low beams, or DRLs by turning the switch to the left of "auto". Could you take a pic of your switch, just for my own curiosity? Turning the switch 2 clicks to the right should turn the low beams on, when they are off. So I assume, with someone looking at the front of the truck, you don't see a change between DRLs and low beams when the switch is activated during the day?
 

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