Vehicle: Most vehicles, especially with 2.7L engine (LX) (JR)
Concern: The MIL (check engine light) is on. Scan tool reveals DTC P1281 cooling system performance and/or P0128 thermostat rationality.
Cause: Low coolant. Coolant bottle has not been topped off at normal service intervals.
Resolution: Top off the cooling system with the correct type of coolant. Most late model vehicles require orange coolant. Do not mix coolant types, except in an emergency. Verify that there are no coolant leaks. It is common for the black plastic coolant housing (top front of engine) to leak. Coolant housing has one or two hose connections, coolant temp sensor and bleeder screw.
Details: (3) warm-up cycles will clear the MIL.
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.