P0340 Camshaft Position sensor error, but after water crossing (1 Viewer)

[SHIfTHEAD]

Backstory, about 2 months ago I was driving down the road after a big rain shower and hit a deep water puddle and the truck starting bogging down really badly. Eventually I had to stop and put it into Low range, to be able to get it to be able to pull and going again. It would idle fine, rev fine, but bog down when under load. After a few miles this cleared up and haven't had an issue since till yesterday. Yesterday I went through a big water crossing and shortly after that it started acting the same way again. Idle fine, rev fine in Neutral but bog under load. Put it into Low range and could get it going. If I could keep the RPMs above 2000 or so it seemed OK, but if it dropped below that it would bog down. I had to leave it in Low range for a good while this time, and a few times when it would bog down I could basically pump the gas and it would speed up a bit and eventually get going fast enough to get the RPMs high and it would start driving "fine" again. After about 30 minutes or so it seemed to have cleared up and would pull in High range again. This morning I woke up and started the truck and it was running very rough, didn't want to rev, CEL came on and eventually died. Pulled the codes and found a P0340 Cam Position Sensor fault. It's very strange as we looked under the hood when it was initially giving me trouble and found no water had gotten up near the top of the engine. The water crossing came up to about the bottom of the doors.

I just learned that the Cam Position sensor is part of the Distributor and is around the $500 mark, so just buying that as a troubleshooting measure is a last resort. I'm wondering if it's more likely to be water getting into the wiring harness somewhere and causing a short, and the P0340 is a misleading fault code?

 

[SHIfTHEAD]

I just found this post P0340 Post HG - https://forum.ih8mud.com/threads/p0340-post-hg.180367/post-2596107 where @motorsargeT is saying the Cam Position sensor uses the Crankshaft Position sensor as a reference. This makes me think the error code is a red herring and the issue is that Crankshaft Pos Sensor wiring has gotten flooded and is screwing up it's signal. I'm going to check that out tomorrow and see if I can confirm.

 

[SHIfTHEAD]

So I did get under it to check the Crankshaft Position Sensor connection and wiring and found a very dirty/oily connector. With a little effort the connector came apart, it seemed to me to come apart a little too easily for a watertight connector. Makes me think that all those years the previous owner ignored the leaking oil pump seal that saturated the underside of the truck, that this oil may have damaged the internal seal for this connector. I found evidence of oil inside the connector, which means that water can get in too. No green crud in there, but clearly not water tight. So I'm unsure what do to do resolve this issue. Can I get a new loom side connector that has the oring in it and solder on a new connector? Once I cleaned it out with a bit of brake clean a few times and blasted it with air and let it dry, I reconnected it. Initially it still ran poorly so I thought I'd check inside the distributor cap to see if oil is in there. In so doing the coil wire broke off inside the cap, so I have a new cap/rotor/coil wire on the way. But after I reconnected the distributor, and unplugged the battery for a couple minutes, now it all runs smooth as butter.

So I think the main problem is the signal coming from the Crankshaft position sensor is garbled because of ingress of water/oil, which would cause the reference the Camshaft sensor is using to be off. So I need to chase down a way to make that connector waterproof again or find a way to replace it.

 

[BILT4ME]

So I did get under it to check the Crankshaft Position Sensor connection and wiring and found a very dirty/oily connector. With a little effort the connector came apart, it seemed to me to come apart a little too easily for a watertight connector. Makes me think that all those years the previous owner ignored the leaking oil pump seal that saturated the underside of the truck, that this oil may have damaged the internal seal for this connector. I found evidence of oil inside the connector, which means that water can get in too. No green crud in there, but clearly not water tight. So I'm unsure what do to do resolve this issue. Can I get a new loom side connector that has the oring in it and solder on a new connector? Once I cleaned it out with a bit of brake clean a few times and blasted it with air and let it dry, I reconnected it. Initially it still ran poorly so I thought I'd check inside the distributor cap to see if oil is in there. In so doing the coil wire broke off inside the cap, so I have a new cap/rotor/coil wire on the way. But after I reconnected the distributor, and unplugged the battery for a couple minutes, now it all runs smooth as butter.

So I think the main problem is the signal coming from the Crankshaft position sensor is garbled because of ingress of water/oil, which would cause the reference the Camshaft sensor is using to be off. So I need to chase down a way to make that connector waterproof again or find a way to replace it.

Use dielectric grease on the seal around the connector. Be liberal around the edges, but not where the pins are. Make sure it snaps back together securely.

 

[raisinhell2]

You can still buy the plugs new from Toyota.. I have replaced a few of them .

 

[SHIfTHEAD]

So I think I've made some major headway on this issue, rather issues. It seems I had two issues, just my luck. First, the P0340 error; that is going to have been caused by the flooding of the Crankshaft Position Sensor plug. This problem did contribute to the engine running worse than just what the other problem caused. That's because it screws up the ignition timing and I could hear the knocking when the code was present. Watching the advance timing in the Torque app I could see the timing was out of whack. However, once the plug largely dried out the P0340 went away and hasn't come back. However, the other issue was still present, and this is the one that causes the engine to fall flat on its face.

I had been watching the short and long term fuel trends in the Torque app and didn't see anything crazy. From my understanding is that when these are usually flat idling and running at a constant speed, but will vary as throttle changes. That's a generalization I know, but this is the general behavior I was seeing. I wondered if a flooded O2 sensor might cause this issue, but couldn't understand how one could still be wet now, well after the creek crossing. Nevertheless I pulled up the O2 volts front and rear. The front sensor was doing what they do, shows a constant sine wave that varies based on throttle input. However the rear 02 sensor was not doing this, rather it was flat. When I would apply throttle it would increase the baseline and stay flat at this new baseline. Eventually it would fall, or not, or it might fall to the bottom of the graph and not increase with throttle. It was erratic. It was a generic o2 sensor I had to change in Utah when a rock jumped up and broke off the previous one. It worked then, but apparently the water was damaging this sensor, and eventually it was just bad. I cut the 4 wires to the sensor and saw that the voltage dropped to 0 for this sensor. Suddenly the engine was running much better and had it's power back, at least most of it.

So basically the rear 02 sensor was sending bad signals to the ECU with made the ECU think the truck was running extremely rich and it would cut the fuel to the engine. So the new 02 sensor should be here in a few days, and I'll see how it runs after that. RIght now it's been running fine, without the o2 sensor, but too soon to say if it has had any impact on the fuel economy. However, I do have the CEL for the missing 02 sensor now.

 

[CharlieS]

When you cut the wire to the O2 sensor, doesn't that send the ECU into open loop mode and mask sensor problems?

 

[SHIfTHEAD]

When you cut the wire to the O2 sensor, doesn't that send the ECU into open loop mode and mask sensor problems?

Yeah, that's what i was hoping for and it appeared to force the ECU into a baseline function or just ignored that O2 sensor.

But I wouldn't think that would ignore other sensors.

 

[CharlieS]

Yeah, that's what i was hoping for and it appeared to force the ECU into a baseline function or just ignored that O2 sensor.

But I wouldn't think that would ignore other sensors.

I (probably incorrectly) thought that this mode ignored sensor inputs and dropped to a base fuel map.

 

[SHIfTHEAD]

To close the loop on this one, the new O2 sensor has been installed. I noticed the engine runs smoother during warmup. Also it has better power while the engine is heating up as well, and the CEL is cleared, of course. But in general the second O2 sensor didn't appear to change the running of the engine that much. I'll see if a new rear O2 sensor makes any impact on gas mileage, but didn't see any measurable difference with it disconnected. But it could have been going bad for a while. Now I am seeing the proper sine wave behavior for that sensor, so we will see.