Another P0340 code issue, camshaft position sensor circuit.

Hello all,

Looking for some input. I have a 2000 tundra that is throwing a P0340 code. Camshaft position sensor circuit.

When i can get it to start, it idles extremely rough (I started it yesterday after getting a battery in it and it started right up, after changing camshaft position sensor, i couldn't get it to start. Started today though).

Initially when i put a OBD on it, it was misfiring multiple cylinders and throwing the camshaft position sensor code. I went and got a new camshaft position sensor and replaced it (turns out the sensor wasn't the issue, tested the sensor and it has continuity and produces a signal when measuring volts. Also, ground is good on truck side plug of the sensor)

I did a bunch of research last night and suspected the crankshaft positions sensor was bad as it was cranking but not starting after changing the camshaft sensor. Today, I pulled the crankshaft position sensor and tested it. Seems to be working fine, truck side plug has ground as well. After putting the crankshaft sensor back into it, I tried starting it and it did start. still idles extremely rough, check engine light came on so i ran the OBD on it and it threw the P0340 code. No misfire codes this time though.

I know the fuel pump is good, I jumped the relay plug in the fuse box. I also tested the fuel pump relay itself and it clicks when energized and has all the right continuity and resistance. I checked the resistance of the fuel pump resistor just below the fuse box and it came back good with 0.7 Ohms.

Not really sure where to look next. I was thinking of checking the connection between the ECM and the camshaft position sensor? Found a wiring diagram in the FSM but haven't be able to make sense of it yet or how it would help me troubleshoot the issue.

Here are screen shots from the OBD test results as well as the freeze frame:


I honestly don't know what alll the freeze frame info means.

Any input here fellas? Thanks in advance

 

A too-common problem with these trucks is the crqnkshaft position sensor gets misrouted when timing belt is changed. Find the “so you just bought a first gen” sticky thread for links to pics of the damage, proper routing, and other info on this.

I’d ask you: is your harness routed correctly? Is the harness damaged by a belt?

 

Did some more digging and yes, all the wiring is routed correctly. none of the wires are damaged by timing or serpentine belt. I checked the continuity of the camshaft and crankshaft position sensors circuits at the ECM E7 plug and they are both good. I should have checked the camshaft timing pulley today while I had the timing belt cover off but I will do that next. Is a bad ECM likely? The FSM manual says the problems areas are the sensor, sensor circuit, camshaft, and ECM. I would imagine with a broken camshaft or bad ECM the truck wouldn't even start?

 

Freeze frame it just a snapshot of those data points at the exact time it throws the code.
I have a 2000 as well, just went out and fired mine up and took a screen cap of what I see when it's cold, and the fuel system is in "open loop"
It was 89deg here today, so ECT started out pretty warm. My truck also warm idles at around 900rpm, but other than that runs perfectly fine.
This might not help you figure out your code, but I did notice some weird things like your IAT at 91 and ECT 66.... on a cold start "open loop" situation.
Oh, and engine load 29.4 but your idling @ 755rpm. Anyway, here's a same year truck for comparison.

 

Oh, and to answer your question, YES, the truck can run if the ECM is going bad. Chased a no code stall at stop lights for a long time and it disappeared when I replaced the ECM.

 

Stupid question, but have you checked to confirm you didn’t have a water intrusion problem into the ECU? We’ve seen it before. Easy check. Before you mess with the ECU much, jot* down the 10-digit hyphenated part number. They have a penchant for rubbing off at this age. It’s a clamshell that can be opened. I can show pics of what water damage looks like, it’s linked in the megathread.

Just think it’s a good idea to rule out, and if you can pull that part number, you can pick up a new ECU from FS1 or fleaBay for cheap enough.

 

Thanks guys, I appreciate your input. The Calc load was even higher today, 34.1%. The first freeze frame data I took was on a pretty hot day so the 91 degree intake temp is understandable. Is there a way to test the ECM with a multimeter? Thanks again guys.

 

Oof good question. You have a copy of the FSM from the megathread, right? It’d be the 1st place I’d look for troubleshooting, it gives the play by play. I’m on mobile so not easy for me to look.

 

ECT at startup shouldn't read much if any lower than ambient/outside air temperature. How much warmer than 66 was it outside?
I'm guessing upper 80s if your MAF sensor was reading 91 IAT. Easy and cheap to replace those sensors, I did both of mine... 24yrs is a good run.
Facing the front of the engine, left bank/up front/next to the first injector.


I wouldn't poke around the ECM with a multimeter. What you are looking for is corrosion on any of the pins/contacts, or any signs of water intrusion.

EDIT: you could absolutely check continuity from the ECM plugs out to the sensors once you get the pin-out (know what wires go where), but I wouldn't touch those pins on the actual ECM module... but that's just me

 

Yea, after doing some reading, testing the ecm isn't something I would want to do. I am just at such a loss for what is wrong. Do I buy the ECM without knowing for sure if it's the issue?

Full disclosure, this truck has been sitting for about 4 years. Ran like a dream when it was parked. Obviously, a lot can happen in 4 years of sitting. I used a fuel system cleaner and a fuel conditioner with the half a tank of gas that was still in it. Can bad gas throw a code like this?

 

4 year old gas!?

Pump some gas out and fill a glass jar, let it sit, water will settle to the bottom.... that will tell you how bad it is.
If you like playing with fire, you can dump a little on concrete and then try to light it, if it doesn't just flash and burn.... it's watered down.
It won't fix your CODE, but I would drain that tank, either scope it to see how much rust is in there, or drop it, clean it, clean your pump and pickup sock, flush your lines, and start fresh.



This was my tank after the 6-ish years the truck sat before I bought it. I cut it up to dispose of it.



The top of our tanks like to get rusty too, right where the pump is installed, and will let water in.
So get some eyes on that too if you pull the tank.


I guess you can scratch all I've said if it was stored inside, in a climate controlled environment

 

Hahaha yea, it's not ideal. To my defense, I did change the fuel filter before I tried starting it. Looks like there might be some water in the tank. The old fuel does ignite quite vigorously lol.

I checked every cylinder for spark today and they all have spark. However, there were a couple injectors that leaked a fair bit of gas when I disconnected the electrical connector on them. I assume that is not normal?

I got the truck to start when i first tried after it sat for a week. It had a horribly rough idle still. While it was idling I tried to give it some gas and it actually smoothed out a bit. Tried holding it at about 1000 RPM's but it struggled and sputtered and finally died after about 30 seconds or so and I haven't been able to get it to even start since. This has happened the past few times I've worked on it. It will crank and every now and then sounds like it almost wants to start but doesn't.

I opened the ECM today and it looks prestine, no corrosion or anything.

The fuel pump works, there is spark, I haven't found any bad/chewed wiring...

Gas is questionable, and injectors might need an overhaul. Other than that, where else should I look?

Appreciate all of your input, @BroHon and @shifty`

 

4 years, that’s kinda a very important detail doncha think?!

Pore over the whole truck looking for evidence of rodent damage unless this truck was somehow in a magic area that never, ever sees rodents. I would also check, as is seen in the sticky thread, “So… you just bought a 1st gen”, there is an issue with the early years shredding wires on the camshaft position sensor under the drivers side timing cover that’s easily fixed, and you maybe had rodents nesting in there too. Typically they go for under the manifold and on top of the gas tank, under manifold leads to no-start and knock sensor codes (both are under there), on top of tank leads to no gas.

Huge mistake running that truck with 4yo gas, even for a minute. Especially with the ethanol content of modern gas. It’ll eat thru aluminum. It’ll leave precipitate in the filter:

Look. If I were you, I’d be doing this before I went any farther.

Go to the dealer. Get a new OEM gas filter. You do not want to use aftermarket, they’re too restrictive and clog, OEM flows better, as Toyota designed for this engine. So much so they removed the fuel filter entirely in 2005.

Go to the gas station. Fill a 5 gallon gas can specifically with the highest 90-something octane gas you can get in your area. IF you have a Buccees nearby or access to no-ethanol fuel, do that in high octane. Stop by the auto parts store on the way home and grab a can of Seafoam High Mile, and pour it into the gas can.

Pull the negative battery cable. We want to leave it off at least 5-10 minutes to clear the ECU.

Drain the tank. Uninstall the fuel filter from the frame rail. Reattach the negative battery cable. Turn the engine over several times, I’m hoping to encourage the fuel pump to cough up any residual shit and fuel in the tank and burn off whatever is in the rails.

Remove the negative battery cable again. Again, want to leave off for 5-10 minutes while installing the fuel filter.

Install the fuel filter. Pour the gas can gas into the tank. Reinstall negative battery cable. Start the truck and let it idle only for 5 minutes. It may throw codes, that’s fine. You just want to get clean, high octane fuel in the lines and pump and rails, and highly treated fuel thru the injectors.

Turn the truck off. Pop off the drivers side timing cover. Check the cam position sensor and its wiring. Take a pic, I wanna see it. 10mm to pop off the cover. You may need to remove the intake elbow to get clearer access.

If you have a snake cam/bore cam/bore scope, look under the manifold for nesting material. Also, look on top of the gas tank for chewing evidence.

Some people are going to be shocked I am telling anyone to replace the fuel filter. But given how much shit you probably just put thru it, it’s preventative damage control at this point.

 

PS - it is 100% normal for the truck to run rough after removing power for 5-10 minutes. *Especially* if the throttle body is gunked* up. It’s because that length of power loss causes the ECU to reset, fall back to fail-safe running parameters. Until it relearns it can run roughly. Normal.

Only clean the throttle body specifically with marked throttle body cleaner. Do not spray anything into the throttle body. Don’t force or wedge open the butterfly. Don’t let the butterfly slam shut. Spray the TB cleaner into a cloth and wipe.

You may want to clean the MAF also. Only use specifically marked MAF cleaner. Empty half a can all up in it, all over its sensor. Give the MAF 20mins to return to ambient temp before reinstall.

 

Okay. That is what I'll do.

Any suggestions on draining the tank? Should I drop the tank and all that?

I initially was going to drain the tank with the fuel pump by pulling the fuel filter and hooking the the tank side fuel line up to a hose then jumping the relay to turn on the pump. Should I not do that?

Fuel injectors? Should I worry about them right now at all?

 

This sounds great to me.

I wouldn't sweat that situation just yet.

 

Got it. That is what I'll do. Thanks shifty, I will report back.

 

@shifty` @BroHon

I got all the old gas out. Installed OEM fuel filter. Put in 5 gallons of treated gas. Cleaned MAF. Cleaned throttle body.

The truck started up, ran better for sure. Still pretty rough. Threw the P0340 code then dropped idle rpm until it died and can't get running again. Basically, the same symptoms as before but did run better when it was running.

The freeze frame data shows the calc load at 28% so I suspect the high calc load before was from the bad gas.

Tried to take pictures of the cam sensor. Hopefully you can make sense of them. I am 100% positive there are no broken wires on the cam sensor circuit. I've had that damn thing apart probably 10 times. The wiring is good.

Any ideas?

 

Looks like someone misrouted something, and was in there patching up and re-taping harnesses.

I'm sad to say, what I'd be doing next, is confirming my wire routing, and checking all of those (freshly taped?) sections to see what rubbed through and where.

 

PS - the camshaft sensor and tail looks good, sensor looks pretty new too, do you see the "DENSO" casting on it?

This is what we've seen from nicks in the past: https://www.tundras.com/threads/p0340-code-camshaft-position-sensor.95343/#post-2413765

Another example: https://www.tundras.com/threads/p0340-code-camshaft-position-sensor.95343/#post-2445758

And here was an extreme case, I've seen a couple like this now where the wiring was toast/re-spliced: https://www.tundras.com/threads/p0340-code-camshaft-position-sensor.95343/#post-3155147

Next thing I'd do is grab the FSM, and test the camshaft position sensor directly at the sensor, then test from the ECM harness to see if you see similar results. If not, you know this is a wiring fuck-up, probably a PO trying to fix a wire misrouting disaster.

 

The fresh electrical tape is from me. I took the harness apart looking for a shorted wire. All the way from the crankshaft position sensor to where the cam sensor and crank sensor run into the main harness and put the harness back together.

I've done resistance and continuity tests on both sensors, and circuits to the ECM. They are good. Both sensors produce voltage when they pass metal objects.

I am really beginning to think it's the ECM. The truck starts when it's been sitting a while(like several days), then after it throws the code and dies, it will just crank and won't start.

 

@shifty`

I forget where I found this manual, but it was pretty helpful for testing the sensors at the ECM.

 

One guy I watch (Eric O. / South Main Auto / You tube) is a master at tracking down electrical gremlins and broken wires. I've seen him use a mini oscilloscope to verify proper signal.
It would be nice to back probe at the connector on the CamSensor up front and see what signal you have there, then do the same at the ECM. Back probe because I'm not sure if it will start unplugged.
If you had the same/good signal at the sensor plug and the ECM then I'de check the pins on the ECM for corrosion (which I think you did), and if those were fine the ECM would be the next logical step.

 

If you truly believe it's the ECM, and you feel you've followed the FSM on testing necessary wires, and you've reviewed the EWD to verify circuits that could be impacted OR you feel that time is money and/or have more money than time and want to parts-cannon in this one thing, I think I mentioned it prior but FS1 is a good source. Pull your ECU and take a pic of the label with the part@# in format of #####-##### (example below, first digits often "89661-XXXXX") and search for that specific part number at their site. Buying from them, you'll get a certified refurb, and worst-case, it doesn't solve the issue, you can resell on fleaBay.

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