2002 4x4 4.7 SLT - after 10 to 20 minutes of driving, the tachometer starts jumping and engine stumbles or dies. I can turn the ignition on without starting the engine and watch the tach jump and listen to the injectors spaz intermittantly under the hood. Raw fuel will exit the exhaust when trying to start during this electrical tantrum. Codes P0320 and P1299 were present the first time so I replaced the crank sensor and erased the codes. 20min into test-drive the problem reoccured with codes P0320 P0700 P0725. Is this an indication of an electron issue in the engine compartment or in the PCM? or...?

any help will be appreciated!
yam

 

Welcome to the forum!


P0320 No Crank Ref Signal at PCM
P1299 Vacuum Leak Found (IAC Fully Seated)
P0700 EATX Ctrller DTC Present
P0725 Engine Speed Input Circ


With all these erratic codes and your discribtion, I would tell you to go straight to the PCM. You can pick them up on Ebay (Pre-Flashed) and ready for direct install with lifetime warranties for like $200.

 

Thanks for verifying my guess 'shocker, E-Bay... here I come!

yam

 

Please update with results?

 

After replacing the computer it had the same problem. I bit the proverbial bullet and took it to the dealer. $223 later, the problem was fix by replacing the cam sensor. They said it was a tough diagnosis but I am sure that by replacing the computer and crank sensor, they new to look else where.

Kirk

 

just an fyi, if you have a DVOM (digital volt ohm meter) you can switch it to ac (alternating current) & use this setting to check pulse type sensors. it's not very accurate but it will tell you if their totally dead. you will get an ac voltage reading from a good sensor open line from a dead one. It's crude but works in a pinch if you don't have a scope.

 

Still think there's something else going on.

 

Had the same problem happen today. A buddy of mine said do the Crank and Cam sensors. I put in a crank sensor, didn't fix it. I'll try the cam sensor this week.

Then there's this. This is gonna be fun.
https://dodgeforum.com/forum/1st-gen...d-p0725-2.html

 

The next day I put a cam sensor and TPS (since I just got it in this was a good time to do it) on and let it idle for about 20 minutes. No problems. Let it idle today after work for a few minutes too. I'll drive it tomorrow to see if it's in fact fixed.

 

Drove it 7 miles today with no problems.