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My best guess is an intermittently failing cam position sensor (or a problem with its wires/connector - but most likely the sensor itself). On LH forums over the years, it was discovered that when the cam position sensor is on its way out, the cruise control will start turning itself off (apparently something built into the PCM firmware for some engineering reason when cam sensor signal disappears).

You may want to go ahead and replace the cam sensor and the crank position sensor. Highly recommended to get from dealer only (or NGK aftermarket) because aftermarket sensors (except for NGK for these) are a gamble.

You could disconnect the cam position sensor temporarily and see if the problem goes away while it's disconnected. Be aware that if you do that, the engine won't run above 2500 rpm as the timing runs off of the crank sensor below 2500, and switches over to the cam sensor above 2500. Running without the cam sensor won't hurt anything. But it may save time just to go ahead and replace the cam and crank sensors.

The codes you are getting may be because when the cam sensor is acting up, it is pulling down ("soft shorting") the 5 volt power to all the sensors and the PCM just sees other sensors not working properly but doesn't necessarily know why.

Can't guarantee that it's the cam sensor, but fairly certain.

You might also temporarily disconnect the a.c. pressure transducer connector. That sensor is known for failing and shorting out the 5 volt sensor power bus and causing the engine to cut off. I don't think that is your problem because the cruise control turning itself off points to the cam sensor, but you could rule out the a.c. pressure transducer as being the problem.
 

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Actually, it's interesting that you mention the RPM's determining which sensor is used for timing. When I'm driving down the road and it starts bucking, it will quit bucking if I accelerate hard. Maybe it's the crank sensor instead of the cam sensor because when I press hard on the accelerator and my RPM's go above 2,500 it smooths out? I may go ahead and replace them both.
Could be.
 

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You know that your timing chain/cams is correct?

I don't know what the chances of using non-NGK aftermarket sensors would be causing any remaining problem. Just keep that in your mind as you continue your troubleshooting.
 

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So I read this morning that there may need to be a "relearning" process for a new cam sensor. I put the brand new one back in and disconnected the negative terminal on my battery for about an hour. When I drove it around the block, it did fine for about a half a mile. Then when I stopped at a gas station, it died and threw a P0344 code again. I took it back out and put my old one back in to drive back to work. It is missing like it used to, but it hasn't thrown a code that will stick yet. I'm going to wait til it does and check it. It will be interesting if it is the old P0121 code instead of a cam sensor code. Will update once complete.

*Note- there is no one around who has a NGK/NTK sensor in stock. I would have to wait til next week to get one shipped. I am using other brands to see if I can get anything figured out sooner. I will be shocked if I get a NGK sensor next week and my problems go away.
Local dealer part? (more $$?)
 

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the tach is driven from the output sensor. I cant say those sensors he replaced are good or not. I did not read all the chatter but I cant tell you the Map sensor might make the car run like **** but would have nothing to do with the tach.

there was an issue that cause a cascade of codes.. related to 5v if i remember correctly a failing cam or crank sensor would cause what they had started with a cluster of codes. correlation is not causation... the problems could have been happening side by side.
Yet, in his video, the tach is steady, but speedo periodically drops out.

BTW - isn't tach driven by input speed sensor and speedo is driven by output speed sensor?

Who's on first? 🤪
 

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sorry dyslexic moment. tach =spedo
Not a problem. Notice that the OP does say in his first post that the tach periodically drops to zero when the problem is occurring. This is one of those problems that has what appear to be nonsensical symptoms, but that after the cause is found and fixed will make total sense.

One of the difficulties is that the problem is intermittent - got to catch it in the act to measure the failure.

At this point, can't rule out a bad PCM (bad 5 volt bus) or battery (internally shorting - though would expect to see the cluster battery light flickering if that were the case). I hate to introduce more variables without solid solution(s), but could be a bad ground or power connection, loose fuse socket teminal or connector terminal - might be worth removing fuses and de-mating PCM connectors and then reseating.

Might try temporarily disconnecting the headlight switch, as those have been found to cause phantom problems in the past.
 

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Your question about the coincidence of this starting when you did the work is understandable. For some reason it is not unusual for a timing sensor to start giving problems after timing belt or chain replacement unrelated to wiring issues. It doesn't make sense, but that has always been puzzling.

Sure would be nice if the new OEM sensor fixes it. No use speculating. Fingers crossed!
 
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