Help me understand this truck

[Jaxgapn2]

Hi, I have a 2002 dodge ram 1500 4.7 that I am about to lose my mind over. To begin with, cylinder 2 has low compression so I get the 302 code once in a while. My chk engine comes on, then goes off in a couple days. I personally can't tell the difference in the way it drives. I can't afford to get it fixed tho. Now all the sudden I get a code of 320 & 725. Remember, I don't know anything about cars/truck repair, but I do read up on whatever I am having issues with in hopes to understand it. I have my own cheap obd 2 scanner. To my understanding, there could be several different things causing this code. So I take it to a mechanic tell him my codes hoping he can narrow down the specific part. He tells me it's the engine speed sensor. He tells me to call around to get that part. I call around. & find that there is no such part called "engine speed sensor. There is wheel speed sensors, vehicle speed sensors, transmission speed sensors. Some people refer to some of them as the engine speed sensor, but they are not the same thing. I am very confused. Anyway, everything I have read comes down to the camshaft position sensor, & the crankshaft position sensor. I replaced them, cleaned my battery post, (which erased the codes) & drove around my neighborhood for a while to see if the codes came up again. Drove great for a little bit, then started jerking when it shifted, but no code came up. So I bought the transmission input sensor, not sure that's what it's called. Replaced it. Then I wonder if I am supposed to reset it again or not. I then read something about the other sensors need to relearn. What the hell is that? I drove it again, staying close to home just in case. It started off a little rough, the got better. Just about the time I started to think it's all good, it starts jerking again. I just parked it. I cannot find the answers I am looking for. Am I supposed to reset it? How do I relearn the sensors? Is there something else I am missing? I did ask if the low compression had anything to do with it, & I was told it didn't. I am missing a lot of work because of this. Someone please help me out with answers that are specific to my truck that I can understand. Thanks.

 

[GTyankee]

As a first step, take the Negative clamp off the battery for a few hours

 

[Daw14]

Did you purchase OEM sensors ? Aftermarket may cost less when first bought ,but when you have to replace them with OEM , everything you thought you saved is gone. Always buy the sensors that originally came with the vehicle.

 

[mullet6577]

You'll probably have better luck posting in the 3rd Gen section instead of the "how to use the forum" section

3rd Gen : 2002 - 2008

Discuss anything about your 3rd generation Dodge Ram truck here.

www.ramforum.com

 

[Jaxgapn2]

Thank you. I have never even used a forum.

 

[GTyankee]

What are the Possible Causes of the DTC P0725?
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

Faulty Crankshaft Position (CKP) Sensor
Crankshaft Position (CKP) Sensor harness is open or shorted
Crankshaft Position (CKP) Sensor circuit poor electrical connection
Communication error between the Engine Control Module (ECM) and Transmission Control Module (TCM

Code P0725 Description The Engine Control Module (ECM) monitors the engine speed through the Crankshaft Position (CKP) sensor with the engine running, and send signal to the Transmission Control Module (TCM).

Read more: https://www.autocodes.com/p0725.html
..........................................................

another forum members statement

I changed the crankshaft position sensor because it was running a p0340 code and it would rev by itself to about 1200 rpm and back down randomly and had trouble starting.
Since the replacement all those symptoms have vanished but the p0725 code persists. Thanks for any help!

 

[rzr6-4]

Different sensors have different relearn processes but an easy one is to leave the battery unhooked overnight.

Compression sounds like it could be the fabled cam lobe/lifter failure. Would have to pull the valve covers to see for sure.

 

[jws123]

Different sensors have different relearn processes but an easy one is to leave the battery unhooked overnight.

Compression sounds like it could be the fabled cam lobe/lifter failure. Would have to pull the valve covers to see for sure.

Its a 4.7 no cam lobe issue its over head.

Any ways you need to find out why you have low compression on that cylinder first trans wont be happy with a missfiring engine. It is a 4.7 so could be a rocker arm fell off common issue when engines sludge up sometimes ya need a new lifter which is a easy job to do. Or if ya overheated it at any point the valve seat drops a little causing rocker to fall off/compression issues you need to pull the valve cover on that side and have a look.

 

[FabricGATOR]

I don't understand...
Is there a big part of this conversation above my pay grade?

 

[GTyankee]

It appears that some one moved the Original Posters question over to the
3RD Gen section
but the whole conversation was not moved

The original Posters name was

Jaxgapn2 they had a 2002 4.7L​

original Post

USB Outlet Question 2014 2500​

Hi, I have a 2002 dodge ram 1500 4.7 that I am about to lose my mind over. To begin with, cylinder 2 has low compression so I get the 302 code once in a while. My chk engine comes on, then goes off in a couple days. I personally can't tell the difference in the way it drives. I can't afford to...

 

[G-Ride990]

Looks like someone missed something when they moved it originally. Should be fixed now. Thanks for that link GT

 

[markabby]

you can reset codes all you want, but in a couple of days they'll return and usually along with new ones.

 

[Davis MacD]

All the herking & jerking during initial acceleration is usually the crankshaft position sensor.

 

[Mark Harrison]

Hi, I have a 2002 dodge ram 1500 4.7 that I am about to lose my mind over. To begin with, cylinder 2 has low compression so I get the 302 code once in a while. My chk engine comes on, then goes off in a couple days. I personally can't tell the difference in the way it drives. I can't afford to get it fixed tho. Now all the sudden I get a code of 320 & 725. Remember, I don't know anything about cars/truck repair, but I do read up on whatever I am having issues with in hopes to understand it. I have my own cheap obd 2 scanner. To my understanding, there could be several different things causing this code. So I take it to a mechanic tell him my codes hoping he can narrow down the specific part. He tells me it's the engine speed sensor. He tells me to call around to get that part. I call around. & find that there is no such part called "engine speed sensor. There is wheel speed sensors, vehicle speed sensors, transmission speed sensors. Some people refer to some of them as the engine speed sensor, but they are not the same thing. I am very confused. Anyway, everything I have read comes down to the camshaft position sensor, & the crankshaft position sensor. I replaced them, cleaned my battery post, (which erased the codes) & drove around my neighborhood for a while to see if the codes came up again. Drove great for a little bit, then started jerking when it shifted, but no code came up. So I bought the transmission input sensor, not sure that's what it's called. Replaced it. Then I wonder if I am supposed to reset it again or not. I then read something about the other sensors need to relearn. What the hell is that? I drove it again, staying close to home just in case. It started off a little rough, the got better. Just about the time I started to think it's all good, it starts jerking again. I just parked it. I cannot find the answers I am looking for. Am I supposed to reset it? How do I relearn the sensors? Is there something else I am missing? I did ask if the low compression had anything to do with it, & I was told it didn't. I am missing a lot of work because of this. Someone please help me out with answers that are specific to my truck that I can understand. Thanks.

On the compression problem i had a 5L mustang that did that and spent a lot of money at dealer and they found nothing, I pulled the piston out and found burn hole in the piston behind the piston ring so when the ring would rotate around it would lose compression and miss fire until it rotated some more then it ran fine for a while, good luck