2007 Camry V6 Keep getting P0355 code and ruining coils
 

Hey guys. I have a 2007 Camry V6 that keeps getting a P0355 code and I keep ruining coils I put in cyl 5. Here's what I've done so far...

Got a P0355 (misfire on cyl 5) and it ran poorly. I figured it was a bad coil, so I ordered some cheap coils on Amazon. Replaced coil 5 and it ran okay for 2 days before I got another P0355 and the car ran bad again.

Figured it was just a cheap coil and I'll try another. Put a cheapo in cyl 5. Again, ran good for a day and threw P0355 and ran bad.

Figured maybe the plug is causing it. I swapped a spark plug from cyl 2 to cyl 5. Still throws P0355 code.

I had a spare ECU and put that in. Still gets P0355 codes.

Swapped the coil (original part) from Cyl 2 to Cyl 5 (cheapo coil). Got a P0355 that didn't ruin the coil. I cleared the code yesterday and it hasn't come back today.

My only other guess is that the wiring harness to cyl 5 coil may be bad. Does anyone have the procedure to test the coil harness? BTW, the coil has a 4 wire configuration. I know the top wire is 12V, the bottom wire is Ground, and the two middle wires are signal. I read somewhere I would need an oscilloscope to test it, but if there's a way to test with a multimeter, it'd save me some $.

Thanks in advance.

-The Sink

Not up to speed on the 4 wired ign coils for this year/engine, but.

Start by checking a number of cylinders for the info below to get a feel of what are "normal" readings..

Use ohm meter to check for wiring shorts or open circuit.

Check for open resistance of the ground terminal on the harness plug. Should be 1 ohm or less. Check for shorts to ground. Should be 10K ohm or higher. Note that the ground wires for all coils may be ganged together then run to chassis ground.

Check voltage of harness 12v wire. Should be battery voltage.

Disconnect wiring harness at ECU. Check resistance of wiring between the plug end terminals for the two center terminals (wiring between coil plug and ECU plug). Should be 1 ohm or less. Check for shorts to ground. Should be 10K ohm or higher. Note, one of the 2 center terminals wires (the one for the IGF circuit) may ganged with the other coil IGF terminals then connected to the ECU at one location..

The IGT circuits is what triggers the ign. The IGF circuit is the return confirmation signal. Typically the ECU grounds a circuit to complete it. The ECU activates to send a high signal to IGT input of coil, assuming by grounding that wire. The coil fires then sends a low signal back to ECU via the IGT circuit. If the IGT circuit low pulses are not in sync with the high pluses (for all coils) then there is a problem. The ECU can determine what coil is the problem by timing things, crank position, etc.

Since you swapped the ECU it appears a wiring issue. Make sure the harness plug terminals s are clean, etc.

There have been complaints about cheap coils having problems.

Thanks for the well-written explanation. I'll find the pin-outs for the ECU side and test as you said. The connector at the coil has a broken tab so I'm going to swap the outer plastic and I'll check for any corrosion then. I'll post my findings.

https://cimg8.ibsrv.net/gimg/www.cam...5ff4e3f7ff.jpg
I found a good pinout for my ECU, even though it's shared with a rav4. Looks like the IGT1 through IGT6 circuits are on pins 35 through 40 and the IGF is on pin 106. I plan to dig out the multimeter in the next few days and test.

Toyota has a website that offers access to factory service info. One can get a 2 day access for $20.

https://techinfo.toyota.com

Figured it out!
 

The problem wasn't so bad for a few weeks. The car would shudder for a second and throw the error code, so I kept an OBD2 reader connected just to clear it. I finally got sick of it so I cut off the connector to the #5 coil and spliced in a new one. No more shudders or errors. It was the connector the whole time. Thanks for the advice.