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P0340 CMP (Camshaft Position Sensor) Circuit Failure

04-19-2004, 03:47 PM
Hi guys, my mother has a 1999 Camry 4cyl. that has code P0340. She says that she was driving down the road and felt like a misfire, saw the MIL turn on. When she let off the gas, she said the car stalled. It is a crank no start issue now. I was able to pull the code, but really am not familiar with Toyotas in General. I am mechanically inclined but do not have access to media such as All Data or a Service manual. Does anyone know if this is most likely the sensor itself or more of an ECU issue? We cannot afford to have it towed or diagnosed by any shop right now, so if anyone could help me in either diagnostic procedures or experiences, it would help us out a lot.

Joe W
04-19-2004, 03:50 PM
It is more than likely the sensor or the wiring leading to it.

04-19-2004, 04:15 PM
Thanks Joe W. There should be a way to test the sensor right? Kind of like testing a wheel speed sensor on ABS, where you measure voltage or resistance (can't remember) through the connector as you pass a screwdriver or some metal object near the sensor. Although I think the CMP is a hall effect sensor, but should still be able to be tested using the same method. Also, is the sensor located on the right side of the head (opposite the side of the belts) w/ a single wire blk/ylw or ylw/black I think?

Joe W
04-20-2004, 03:47 PM
The sensor is located on the backside of the cyl.head and is hard to access,but is tested by checking resistance.There are 2 wires to this and they should be blue and blk/white.A cold sensor will give a reading of 835-1400 ohms.Hope this helps.

04-20-2004, 04:24 PM
Left (belt)side. Give it a professional jiggle and try it before taking it apart.

04-20-2004, 09:46 PM
okay, here's what I've found out. I was able to acquire technical information and tested the resistance of the cam sensor (cold) and was within specs. I also had a wiring diagram of where it connected into the ECU. There is continuity in the wires from CMP to the ECU. In the diagram, it shows the CMP splicing and using the same positive wire as the Crank Sensor. I checked crank sensor resistance and it was out of spec by about 400 ohms. Spec called for 985-1600 ohms and I got 2023 ohms. Now I know that the DTC that was recorded was for camshaft sensor circuit failure, but wouldn't it also be possible to have this code, but actually have the crank sensor be the fault; since they do share a wire and technically are within the same circuit. I know the ECU uses both the cam and crank sensor referrence to determine no.1 cylinder position. Before this problem happened, I did notice a grinding noise similar to the timing belt rubbing against the engine cover. It could be possible that ground up t-belt rubber accumulating on the bottom on the crank sensor could be a possibility; although it shouldn't affect resistance of the sensor because this is internal resistance. I don't know. I'll have to tear down the belts, remove crank pulley and engine covers to see what's going on. Sorry for the long rant, but if anyone else has any opinions, thoughts, or experiences, I would appreciate it. Thank You again Joe W. and csaxon for your input

04-21-2004, 01:21 PM
What's your mileage and has the timing belt ever been changed? A DTC indicates a malfunction but not always a part failure. If the cam sensor was within specs then it's probably okay. Check for open circuits or shorts in the wiring harness and connector for the cam and the crank sensors. Check the wiring between the ECM and the sensors. The signal plate for the crankshaft is on the crankshaft and generates 34 signals per revolution so I doubt that some belt fibers would block the signal to the crank sensor. If the crank sensor is out of specs then it needs to be replaced

04-21-2004, 06:43 PM
Okay, here's the deal. I was already suspecting the t-belt to be loose because of the noise. I entertained the idea that it might have skipped a couple of teeth on the cam sprocket and caused the ignition to go haywire. So I took off the upper engine cover to check base timing and found only about half of the t-belt left and the rest in shredded pieces. There was hardly any tension on the belt so I guess the tensioner pulley somehow came loose. The inside of the engine cover was also moist, but not from oil. Maybe the waterpump leaked or seized causing the tensioner lose tension then shredding the t-belt. I have heard that toyota waterpumps sometimes seize because of the orange coolant leaving deposits or something. I never got the chance to check base timing because I am going to have to reset it anyway when I replace the t-belt, waterpump, seals and maybe a bad tensioner. But I'll go out on a limb and say that it did jump teeth causing the crank and cam sensor to be out of sync w/ each other severly retarding the ignition timing. The car only has 45000 miles.

04-21-2004, 08:51 PM
Sorry to hear the news but you confirmed my suspicions. It's highly irregular for the belt to break like that at 45000miles. The belts materials were changed and strengthened at the end of '98 so that the replacement interval for a '99 is now 90,000 miles or 6 years whichever comes first. A seized waterpump could definitely wreak havoc on a belt but you should have had warning signs. Anyway, you have your work cut out for you. I pass through here once in awhile but I'm usually at You might get more help over there.

04-23-2004, 10:35 PM
Well, finally got the new t-belt on. The waterpump pulley had so much play, it wasn't even funny. I also changed the crank seal, oil pump o-ring and seal. The idler pulley was still good but I did replace the tensioner and spring. It was kind of a pain to align the camshaft pulley to set to no. 1., but a mirror solved that problem. When I put it all together and started the car, the t-belt was flapping all over the place and was slapping the engine cover. I am used to honda t-belts where loose is acceptable. I was able to tighten the belt without taking it apart by loosening the tensioner, removing the belt partially, turning the cam pulley clockwise 1 tooth, pull the slack off the belt, reattach t-belt and turn the cam pulley back counter clockwise 1 tooth to reallign no. 1. That took most of the slack out. All is well now. Thank you again for your input Joe W and your help csaxon. I'll have to check out toyotanation sometime.

12-01-2013, 04:00 PM
Greetings same thing happens to me, I know how I've fixed and only speak Spanish

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