3rd cylinder miss with eaten injector harness

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PNWLX

PNWLX

Joined
Jul 24, 2019
Threads
3
Messages
46
Location
Vancouver, WA
06 LX470
Yesterday we noticed she was running a bit rough right as we left the house for the day. Within the block it threw a code so we parked it. Scan gauge said it was a 3rd cylinder miss.

I immediately assumed coil pack, so I swapped it with cylinder 1 to see if the issue followed the coil. Nope, still an issue on 3. Looked a little closer, and there's a peanut sitting right below the injector for #3, and the 2 wire injector harness is eaten away.

I re-pinned the plug with one of out a cheap Amazon injector plug, but the misfire remains. I tried swapping wires, in case I got them backwards when taking everything apart, same deal.

Seemed pretty obvious that the lack of a wire to the injector would cause the miss, but assuming that's fixed what else might have been borked by the mouse or whatever was in there?

nomnom.webp


I assume testing injector resistance, and activity at the plug itself are next, but any other ideas?
 
Check resistance on injector. They are fairly fragile and the messed-up wiring likely fried it.
 
I'd fix wires and see if P03-- clears.
Dealerships will sell you new pig tails (wire leads w/ends) for the wire housing block. You can either unpin old, or just buy new wire housing block.

Heat shrink seal solder butt splice.
 
If it’s still misfiring after fixing the connector, you can get an injector noid light to check the injector pulse from the ecu. Plugs into the injector connector. This circuit is power all the time with ground pulse. I’ve seen commuters damaged because of this.
Hopefully yours didn’t !
 
aztoytec said:
If it’s still misfiring after fixing the connector, you can get an injector noid light to check the injector pulse from the ecu. Plugs into the injector connector. This circuit is power all the time with ground pulse. I’ve seen commuters damaged because of this.
Hopefully yours didn’t !
Click to expand...
Finally got a proper plug with new leads to test with today, just in case my re-pinning of the old one was making for a bad connection. No luck.

Resistance was about 11.3 Ohms, which seemed about the same as the neighboring injector (it's 40F outside). I also applied 12v directly to the injector and can confirm it was clicking, so it doesn't seem stuck.

Still getting the misfire, so I connected a test light and I've got power at one pin, and a very vague-looking ground signal at the other when the truck is running. It almost appears to be flickering, but inconsistently. I tested the next cylinder and it has a very distinctive pulse with the light when running, which is what you would expect to see on a functional cylinder.

Seems like it's pointing to the ignition signal :-(. Is trying to replace the main ECU most likely where we are heading, or is there another controller somewhere in line? I have to assume I'd need to track down a VVTI model ECU, if not specifically a 2006 LX, but are they otherwise coded to the vehicle (thinking of keys, security, etc.)?
 
Unfortunately sounds like you’re on the right track. You will need to reprogram the ecu for the immobilizer. I’m not sure your can be done with a used ecu. Some are different. You will most likely need one same year. There should be a part number on the factory ecu that will help you source one.
 
It does seem risky that a shorted injector wire could cook the ECU... the repair is solid at that obvious point of failure, and I couldn't find any other suspect rodent attacks nearby, but I'll trace it back further tomorrow.

I'll also see how it compares with the outputs on the ECU itself.

Appreciate the tips so far!
1767321275797.webp
 
Trunk Monkey said:
Highly unlikely it's the ECU, that's just not a cause/effect - wire at injector has damage = blown ECU. I would look for wiring damage further up the lin
Click to expand...
If you short or ground out the power wire to the injector, which is from the ecu it will damage the driver inside it. Seen it numerous times. If he’s got no power to the injector or looses the ground pulse, that’s most likely it. Possibly another damage wire from the ecu…but that’s the circuit.
 
I'd for sure check wire(s) resistance from wire housing block at ECU to Fuel inject. Before replacing ECU.
 
AARONTLC said:
^This has to be done.
Click to expand...
Just did this, and finding the same at the ECM. Checked continuity between the wire coming out of the harness and the one at the injector plug first.

I'd note that the problem injector plug (3) shows constant 12v when the ignition is on, where the others don't - as they are awaiting the ground signal from the ECM to complete the circuit. When the truck is running, #3 it still shows constant power, where the neighboring plug you can see the pulsing.

Assuming I got the right wire at the ECM, and again - checked continuity, you can also see it showing a constant ground signal. The neighboring wires to the other injectors are pulsing as expected.

I attempted to record a video of most of this, if it helps uncover any clues:

I really don't see anywhere else the harness is compromised, and it seems unlikely that this same wire that was eaten would also be singled out somewhere else in the harness.

Anyone use a service like UpFix before?
 
PNWLX said:
Just did this, and finding the same at the ECM. Checked continuity between the wire coming out of the harness and the one at the injector plug first.

I'd note that the problem injector plug (3) shows constant 12v when the ignition is on, where the others don't - as they are awaiting the ground signal from the ECM to complete the circuit. When the truck is running, #3 it still shows constant power, where the neighboring plug you can see the pulsing.

Assuming I got the right wire at the ECM, and again - checked continuity, you can also see it showing a constant ground signal. The neighboring wires to the other injectors are pulsing as expected.

I attempted to record a video of most of this, if it helps uncover any clues:

I really don't see anywhere else the harness is compromised, and it seems unlikely that this same wire that was eaten would also be singled out somewhere else in the harness.

Anyone use a service like UpFix before?
Click to expand...

Man, I am sorry. You have a solid 12v at the ecu with no pulse. Which either means the injector wires are completely shorted together bypassing the injector and like @aztoytec said, the mouse has fried the injector output #3.

With this circuit #3 open on both ends, did you check if the 2 wire circuit reads open? Has the signal wire from the ecu to injector been checked for no continuity to chassis ground?

I can’t think of anything else. Wondering if your ecu can be repaired? There are people that do it. Especially if you know what has gone bad. Wishing you best of luck!
 
BTW: Very helpful if: Make, model, year, mileage, mods, etc. Listed in signature line. ;) 06LX 200k mile, stock

I can't see what pins nor do I know off top of my head, which are to be where.

I can't see that you check resistance of each wire from FI to CPU. This would be done battery disconnected. Long jump wire to bridge from wire housing block at FI, to wire housing block at ECM. Point was, to see if wires, all at same resistance. Which would indicate all wire strains in each sheathing making a good clean uninterrupted connection end to end.

The exercise was also to, make sure you'd not mixed up wire placement, as it enters wire housing block at FI. As you'd need to use wire diagrams to indicate which pins at each end to test.

__________________________________________________________ Back to first test of FI. It was a fail. Possibly, FI #3 was damaged by crossing wires.

FI test good. No! "Resistance was about 11.3 Ohms, which seemed about the same as the neighboring injector" What was neighboring ohms reading?
Spec range is 13.4 - 14.2 OHMS at 68F. 11.3 OHMS at 40F observed. Not ideal temp of 68f, but still would expect 12.6 ohms at 40f. According to AI working formulation: 12.6 ohms at 40f, would be equivalent to 13.34 OHMS at 68f.
Replace FI.
FI test good. Yes

If still miss firing. Which a DTC P0303 (cylinder #3 misfire) should be present (pending or current)

Each wire test good with same OHMS, end to end. Yes!
Each wire routed from ECM to FI pin in wire housing block, correctly. Yes!
Signal at FI wire housing block from ECM, as should be. No! test ECM.
 
Last edited:
AARONTLC said:
Man, I am sorry. You have a solid 12v at the ecu with no pulse. Which either means the injector wires are completely shorted together bypassing the injector and like @aztoytec said, the mouse has fried the injector output #3.

With this circuit #3 open on both ends, did you check if the 2 wire circuit reads open? Has the signal wire from the ecu to injector been checked for no continuity to chassis ground?

I can’t think of anything else. Wondering if your ecu can be repaired? There are people that do it. Especially if you know what has gone bad. Wishing you best of luck!
Click to expand...
I had that realization last night that I neglected to test the injector 3 wire with it disconnected at both ends. Did that this morning and re-confirmed the wiring is good. Showed 000.2 Ohms of resistance, which was the same as the neighboring injector (also disconnected from the ECM and the injector itself).


2001LC said:
BTW: Very helpful if: Make, model, year, mileage, mods, etc. Listed in signature line. ;) 06LX 200k mile, stock

I can't see what pins nor do I know off top of my head, which are to be where.

I can't see that you check resistance of each wire from FI to CPU. This would be done battery disconnected. Long jump wire to bridge from wire housing block at FI, to wire housing block at ECM. Point was, to see if wires, all at same resistance. Which would indicate all wire strains in each sheathing making a good clean uninterrupted connection end to end.

The exercise was also to, make sure you'd not mixed up wire placement, as it enters wire housing block at FI. As you'd need to use wire diagrams to indicate which pins at each end to test.

__________________________________________________________ Back to first test of FI. It was a fail. Possibly, FI #3 was damaged by crossing wires.

FI test good. No! "Resistance was about 11.3 Ohms, which seemed about the same as the neighboring injector" What was neighboring ohms reading?
Spec range is 13.4 - 14.2 OHMS at 68F. 11.3 OHMS at 40F observed. Not ideal temp of 68f, but still would expect 12.6 ohms at 40f. According to AI working formulation: 12.6 ohms at 40f, would be equivalent to 13.34 OHMS at 68f.
Replace FI.
FI test good. Yes

If still miss firing. Which a DTC P0303 (cylinder #3 misfire) should be present (pending or current)

Each wire test good with same OHMS, end to end. Yes!
Each wire routed from ECM to FI pin in wire housing block, correctly. Yes!
Signal at FI wire housing block from ECM, as should be. No! test ECM.
Click to expand...
Really appreciate the detailed run through. I think this morning's test confirms the state of the wire between the ECM and the injector plug. I also confirmed that the #3 pin at the ECM goes to ground as soon as the ignition is turned on. The other injector leads don't do this. That said, it doesn't appear to show continuity with the chassis or the case of the ECM itself, but you can read 12v by using that pin as your neg. connection on the meter.

Both injector 3 and injector 5 show 11.5 Ohms on my meter today. I also updated my sig :-).
 
UPDATE (mostly because it's good news, but also hate finding forum posts from years past where we never see if the thing got fixed or not...)

Can't believe it's been exactly a month since this first came up! I reached out to UpFix with what troubleshooting had been done so far and they were very confident in the injector driver as being fried. I sent the ECM in using the label they provided on January 5th, today I received it back. The technician noted the following:
  • Pre-Evaluation: Communication: NO, Corrosion on the pins: NO, Cosmetical damage: NO
  • What was done: Circuit board issues repaired, Final test on work-bench performed, Communicated with unit and cleared codes, On pretest found that the driver for injector #3 was out of spec and shorted. Replaced that driver and now all injectors are reading within spec.
  • Tech Note: On pretest found that the driver for injector #3 was out of spec and shorted. Replaced that driver and now all injectors are reading within spec.
Reinstalled the ECM and reconnected the battery. Fired right up with no errors. Took it around the block and then on a longer trek across town, and sure looks like we are all good.

Really appreciate the tips and help here. Still bumped something so little took us off the road for a month, and $400 to fix, but at least it's fixed.
 
PNWLX said:
UPDATE (mostly because it's good news, but also hate finding forum posts from years past where we never see if the thing got fixed or not...)

Can't believe it's been exactly a month since this first came up! I reached out to UpFix with what troubleshooting had been done so far and they were very confident in the injector driver as being fried. I sent the ECM in using the label they provided on January 5th, today I received it back. The technician noted the following:
  • Pre-Evaluation: Communication: NO, Corrosion on the pins: NO, Cosmetical damage: NO
  • What was done: Circuit board issues repaired, Final test on work-bench performed, Communicated with unit and cleared codes, On pretest found that the driver for injector #3 was out of spec and shorted. Replaced that driver and now all injectors are reading within spec.
  • Tech Note: On pretest found that the driver for injector #3 was out of spec and shorted. Replaced that driver and now all injectors are reading within spec.
Reinstalled the ECM and reconnected the battery. Fired right up with no errors. Took it around the block and then on a longer trek across town, and sure looks like we are all good.

Really appreciate the tips and help here. Still bumped something so little took us off the road for a month, and $400 to fix, but at least it's fixed.
Click to expand...
Great job! No parts cannon fired. Love that!
 
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