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Doug in North Carolina
Doug in North Carolina, ASE Certified Technician
Category: Dodge
Satisfied Customers: 302
Experience:  ASE Master Mechanic, 12 Years Experience Specializing in HVAC, Electrical and Driveability Problems.
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1997 Dodge Ram 1500: V8..the truck check engine light..wont start

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Diagnostic code shows cam sensor problem, but there is no cam sensor in our 1997 Dodge Ram 1500, V8, 5.2 engine, 4 x 4. We replaced instead the crank sensor, but still have the problem. Sometimes the truck check engine light comes on, & it won't start, until we disconnect the battery, then it will start. Sometimes the check engine goes off for a while, then comes back on. We have also replaced the spark plugs & wires, & the distributor cap & rotor was replaced last year. There doesn't seem to be any other symptoms, it seems to run well otherwise. Do you have any suggestions on what we can check?

Thanks for using Just Answer, my name is Doug.


The computer uses a pick-up plate under the rotor button in the distributor to determine camshaft position.


The code that you're addressing, do you have a specific fault code number for it?

Customer: replied 7 years ago.
AutoZone gave us the diagnotic troubleshooting #PO340. Is this the number you need?

Yes. That code does point to the Cam Sensor.


If you have access to a multimeter I can give you instructions on how to check the wiring and computer signals going to the cam sensor. The actual output of this sensor can only be checked accurately by using a meter that can graph the pattern. Most mechanics don't even have one so I wouldn't expect the average vehicle owner to either.


Let me know how you'd like to proceed.


Customer: replied 7 years ago.
We have a multimeter, but this truck supposedly does not have a cam sensor.??
It's a pick-up plate located under the rotor button in the distributor. If I refer to it as a cam sensor then that's what I'm referring to.
Customer: replied 7 years ago.
Ok, how do we proceed to check it, w/the multimeter? If we change the rotor & cap will this take care of the problem, or is it what you are calling the pick-up plate under the rotor, which could be the problem?

Changing the rotor and the cap will not replace the cam sensor/pick-up plate. The Cam sensor/pick-up plate is a component all to itself that is housed in the distributor, under the rotor button. To get to it you will need to remove the cap and the rotor though.


I cannot tell you that replacement of the sensor/plate will fix it. I can provide information on how to check that the sensor is getting everything it needs to in order to send the correct signals. From there you can make your own assesment based on the information you've gathered and what I've provided. Without a lab scope (that graphing meter I referred to) there will be no sure-fire way to verify, before replacement, that the sensor is bad.

Customer: replied 7 years ago.
The multimeter that we have should be the same as a graphing meter? If so, what do we do to check this plate sensor? What should this meter show, if it's bad? or good?

The meter you have PROBABLY does not do graphing. Most graphing meters (oscilliscope/lab scope) like what I'm referring to start at about $1,000.00. If you have a model number then I can research it and tell you if it's capable.


The connector for the harness side should have three wires. With the sensor unplugged, two wires will show 5 volts and the other wire is your ground wire for the sensor. When you plug the connector back in, if you're able to pierce to tap in to the wires, one wire will still show 5 volts but the other one that previously had 5, will now drop. You can use your ground wire for the black lead of your meter while you're checking these voltages.


While you have the meter hooked up to the wiring checking for 5 volts and ground, have someone help you by moving the engine harness around. What we're looking for is a drop in the voltage caused by the rest of the harness rubbing on the engine, shorting with other wires inside the wire loom or signs or oil saturation. Continue monitoring the voltages while the wires get wiggled all the way back to the computer.


The diagrams I have are for a 98 model but they should be fairly close. I can get the correct diagrams (or verify them to be the same) tomorrow.

-Black/Light blue should be the sensor ground

-Violet/White should show 5 volts all the time

-Tan/Yellow should show 5 volts when unplugged and drop when plugged back in.


It's getting late here and I need to knock off for the night. I'll be available again tomorrow night starting at 6:30pm EST. If you have questions during the day I MAY be able to answer them. If you need assistance quicker, I can opt out and another expert can assist you further.


If the information I've provided is helpful, you can click the accept button at any point. I can provide assistance even after you accept the answer.



Customer: replied 7 years ago.
Please send the diagram tomorrow. Anything that you can think of that may be helpful to resolve this problem would be appreciated. Thank you.




Customer: replied 7 years ago.
Thank you. The diagrams should help us now. We clicked on Accept Answer, last night, so that should take care of your help.

I'm not seeing the accept. On my end it shows that you've made a deposit with Just Answer but the funds haven't been transfered to me. A deposit can be added at any time in any amount, the acceptance of an answer is the only thing that transfers funds from your Just Answer account to the expert helping you.


It's still showing that you have 1 question open with 0 accepts.


But before clicking accept again, verify with Just Answer customer service the status of your accept.




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