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Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3404
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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My 2002 dodge dakota 4.7 4x4 crew cab ran fine until I

Customer Question

Hi my 2002 dodge dakota 4.7 4x4 crew cab ran fine until I changed the clutch and in the process damaged and then changed both O2 sensors in the exhaust pipe. The truck now idles fine and seems to run OK at high RPM, however it backfires and sputters on acceleration. I disconnected the battery ground and then attempted to reset the ECU with the key on for 30 seconds and reconnecting and starting. This seems to make no difference. Any suggestions.
Submitted: 1 year ago.
Category: Dodge
Expert:  Dodgerench replied 1 year ago.

Hi, welcome to JustAnswer!. This is Ed.

Check Fuse U in the underhood fuse and relay center, what we call the PDC. This fuse is a basic power feed to both oxygen sensors for heater function, then the PCM (engine controller) grounds the circuit as needed to control current flow. I'm assuming your 02 sensor pigtails got stretched when the exhaust was dropped, which may have caused the power and ground circuits in the 4-wire 02 sensors to come into contact with one another. If the fuse blows, both sensors will run cold and will produce a signal that's similar to that of a very rich running engine. The PCM will respond by pulling fuel from the injection system using reduced pulsewidth, leaving the engine starving for fuel much of the time.

Fuse U of the PDC is a 20 amp mini-fuse, probably identified as "02 SENSOR" in the under-cover road map. It becomes hot only with the engine running, as it's an offshoot of the ASD relay and it becomes energized with engine rotation.

Let me know if you have any questions or problems and I'll be glad to help.