P0340 code --> New ECU

I have a 2003 V6, manual trans with 187K that I bought back in June. The timing belt was changed before I bought it. It is throwing a P0340 code, the Camshaft Position Sensor. I am intermittently having significant power loss. Alldata shows a diagnostic pathway of: replace sensor --> check wiring --> check timing --> replace ECU. I have replaced the sensor. I checked the timing and it was found to be 1 tooth off, so I repositioned the belt. When the code was still present, I took it into my local Toyota dealer for diagnostic, just to see if they had any suggestions. They said all electrical checks out and wanted to get into the timing for $850.00. I said no (since I had already done that). The master tech said that he was pretty sure it might be the crankshaft pulley (behind he harmonic balancer), so I replaced that. When I was placing the timing belt for the 2nd time, I noticed there is some play in the cam shaft pulleys. The bolts are tight to the torque specs, but they rock a little back and forth, and they are easy to turn by hand. (Is it normal for the cam shafts to have some play?) After all that, she's still throwing the code.

Long story short, I'm pretty sure I need an ECU now. Its part number 89661-0Y010-84.

1. Does anyone have any other suggestions on what to try before ECU replacement?

2. I am looking for the ECU which is $804 @ dealer. I have found it as cheap as ~$550 online, but not sure how reputable the sellers are. Are there any reputable sellers on here who would sell it cheaper? Or does anyone have any reputable seller recommendations? I prefer to pick up in person, if possible. I live in central OH.

Thanks in advance for any help or suggestions!

 

It's really really rare for a Toyota ECU to go bad. Does it immediately set code after you clear it?

 

Immediately. Every time. Lately, there's a slight <30 second delay (instead of no delay) in the light.

I took out the ECU a day ago, and even opened up the case. The computer board did not have any obvious signs of damage (but I'm no computer technician...)

 

It's possible the cam pulleys are switched, the right side looks like this and has a small tab that triggers the cam sensor.
Notice the lip on front and back to keep belt on pulley. The drivers side doesn't have the back one.

 

notice tab?

 

They're definitely not switched. the tab is on the correct side with the camshaft position sensor.

 

Take a good look at the sensor connector (hit with some contact cleaner) and the ground near the diagnostic connector. The camshaft signal is analog and is fairly sensitive - wires are shielded.

I have had that ground lug off so many times I think the wires are close to breaking and it seems they run the wires separately for each function to the lug (ignitor, shielding and o2 sensor heaters if I recall correctly). Perhaps you can ohm the shield to EB if you can expose shield.

Also check EB to chassis ground straps, large one near oil filter and small one on passenger side rear cyl head on 3.4L.

 

Update: I rechecked the timing. It looks like the cams could be 1/4 to 1/2 tooth off. Or, it could be my imagination and the timing is fine. It's hard to tell. I cleaned the Camshaft sensor and checked the plugs and ground screw. P0340 code still showing. I Reset the computer by unplugging battery. It took about 20-30 seconds for the code to show. Would the ECU throw the code if I'm potentially only 1/4 to 1/2 off? That timing belt is extremely hard get back on!

 

Are the timing belt tensioner and idler pulleys in good shape. You've unbolted the tension each time and pinned before putting the belt on?

 

I replaced the tensioner the first time we adjusted the timing. I have unbolted and pressed the tensioner each time (there's no way to get the belt back on with out this step). Idler pulley seems to be in good shape.

 

Just what brand sensor some after market ones can be hit or miss.Poor quality pigtails that fail to make a good connection plugging into the truck harness.

Did you check the old cam sensor to see it failed?

I have had good luck with ECM Depot Grand Prairie TX having ECM`s rebuilt.

About the only thing that damages a ECM is water damage and voltage spikes!!

Good Luck.

 

Any luck on what the problem was. My truck is doing the exact same thing

 

Over $3000 later, I have a solution. I had to take it in to the dealership. They did Camshaft Position Sensor electrical circuit test (again), replaced camshaft position sensor (for the 3rd or 4th time), timing belt (again), water pump, thermostat, amongst some other repairs. They wanted to replace the ECU, but I had already done that myself for $600+. A week later, *STILL* having the issue. The service manager called me saying, they have no idea what is causing the issue and will have to involve Toyota engineering. In the end, it was a disconnect in the wiring harness between the ECU & Camshaft Position Sensor. The two were not communicating at all and the ECU was throwing the code and governing the acceleration in order to "protect" the engine.

Bottom line: they did a camshaft sensor wiring circuit overlay, and the code cleared. Power restored. She's driving/accelerating very nicely, and FINALLY a joy to drive!

Frustrating that it took over $3k and several months of time, effort and frustration to fix this problem. Hopefully, my experience will save others time and money! Thanks for all the help.

 

Wow that's terrible, didn't anyone think to put an oscilloscope on it and check the cam and crank signal at the PCM? They could have known in 5 min that the PCM wasn't getting a cam signal, tracing the broken connection down could have taken a bit of time though. Still alot better than firing $3k in parts at it an not fixing it.

 

Yeah, pretty bad. It was the dealership, and as we know, they always find the most expensive way to fix things. That's why I don't trust them, but I had tried so many other things to no avail. I felt like I was up against the wall. I don't know any trustworthy Toyota mechanics in central Ohio. At least it's running now...and still much cheaper that a brand new 'yota!

 

Yea it's so unfortunate that there's so many shops and dealer techs out there that don't do proper testing and instead just replace parts. I realize individuals don't typically have a scope or a sophisticated scan tool but there's no excuse for a shop not to.