Vehicle: All Chrysler/Jeep/Dodge (WJ) (AN) vehicles with 4.7L 8 cyl engine.
Concern: Idle fluctuation. Engine idle speed goes up and down. May be intermittent. Idle speed will rise to about 1200 rpm and settle back to normal. More noticeable in park or neutral.
Cause: The TPS (throttle position sensor) is beginning to fail. The closed throttle voltage reading is not accurate/fluctuates.
Resolution: Replace the TPS located on the throttle body.
Vehicle: All vehicles with 3.7L and 4.7L engines. (WJ) (KJ) (DR) (AN) Jeep Liberty, Grand Cherokee, etc.
Concern: Engine is overheating after cooling system repairs. Engine is overheating after the radiator was drained/refilled for maintenance.
Cause: The cooling system was not properly bled. There is an air pocket trapped, not allowing coolant to circulate.
Resolution: Allow the engine to cool. Remove the bleeder screw. Look where the upper radiator hose attaches to the engine for the bleeder screw. It requires a 10mm hex (Allen) type tool. Sometimes the screw will be very tight. You will need to use a high quality tool and possibly considerable force to remove it. Remove the radiator cap and fill the cooling system until coolant comes out of the bleeder screw hole. Reinstall the bleeder screw. You must use thread sealant to prevent a leak. Put the radiator cap on and retest.
Details: If the bleeder screw will not come out, remove the upper radiator hose at the engine just enough for coolant to come out while filling the system. This will work in a pinch.
Vehicle: All vehicles. (JK)(ZJ)(CS)(JC)(TJ)(XJ)(PT)(KJ)(KK)(KA)(AN)(ND)(DR)(DS)(WJ)(WK)(XK)(LX)(LH)(FJ)(JR)(JS)(RT)(RS)(NS)
Concern: The MIL (check engine light) is on. The scan tool reveals DTC P0601 PCM internal controller failure.
Cause: The PCM (engine computer) has an internal fault.
Resolution: Replace the PCM to correct.
Details: This is an easy diagnosis. When P0601 is present, the solution is always to replace the PCM. There is no other possible cause. Normally the vehicle is still driveable.
Vehicle: All Chrysler, Jeep, and Dodge vehicles. (JK)(ZJ)(CS)(JC)(TJ)(XJ)(PT)(KJ)(KK)(KA)(AN)(ND)(DR)(DS)(WJ)(WK)(XK)(LX)(LH)(FJ)(JR)(JS)(RT)(RS)(NS)
Concern: Alternator failure. The alternator (generator) is not charging. Electrical problems.
Resolution: Hold on for a minute. Alternator failures are extremely rare on Chrysler, Jeep, and Dodge. You need to rule out the battery, wiring, and PCM first before replacing the alternator.
Details: The alternator is controlled by the PCM (engine computer). Again, true alternator failure is very rare. In ten years as a dealer service dept tech, I have replaced maybe five alternators.
Vehicle: 2001 (AN) Dodge Dakota pickup with 3.9L V6
Concern: The MIL (check engine light) is on. Scan tool reveals DTC P0601 Powertrain Control Module (PCM) Internal Controller Failure.
Cause: The PCM has detected an internal fault.
Resolution: The only solution is to replace the PCM. The engine will usually run normally and there will be no driveability issue or other related problems.
Details: The PCM is very easy to replace on this model. It is located under the hood, on the passenger side fender, next to the air filter box. The PCM does not need to be programmed for the engine to run. However, a scan tool should be used to program the VIN and odometer into the new PCM.