Hi Guys,
I have a 99 4.0 153k on it. Installed new radiator 2 years ago. About a week ago I was waiting to pull onto the highway and temp gauge started bouncing around and heard a little hesitation and check engine light came on then off. Drove it for about a week then it happened again at a red light but this time the engine light stayed on with a P0117 code (low voltage to coolant circuit). I did some quick research and was familiar with replacing the temperature sensor to solve a similar issue on another 99. I replaced the sensor and everything was ok for about 3 days. Yesterday at a stop light the gauge started fluctuating again but not as wildly.... I turned on the heater to see if it had any effect but it didn't seem to. I turned onto the highway and it was fine the rest of the way home (no check engine light).
I had read about another guy with the same issue who found that a wire from the sensor in the harness was shorting out on the rear of the engine. I had not disconnected the battery when I replaced the sensor so I decided I would disconnect the battery, clean the terminals and test everything. Everything was good with the battery and alternator...left it disconnected for maybe 15 minutes. I saw that the main harness that goes to the PCM had a spot where it had rubbed through, but the affected wires did not appear to be the ones coming from the ECT. I zip tied it up off the contact point though.
Drove to my dad's and home last night (only about 7 min each way) and work this morning with no issues so far. I'm not confident since the only changes were 1. disconnected the battery and 2. lifting the harness up off of the contact point it was laying on. If this continues, any idea what I should be looking at next? Coolant was changed in 19 when radiator was replaced, reserve tank stays full, no obvious leaks anywhere and good heat with heater on.
I have a 99 4.0 153k on it. Installed new radiator 2 years ago. About a week ago I was waiting to pull onto the highway and temp gauge started bouncing around and heard a little hesitation and check engine light came on then off. Drove it for about a week then it happened again at a red light but this time the engine light stayed on with a P0117 code (low voltage to coolant circuit). I did some quick research and was familiar with replacing the temperature sensor to solve a similar issue on another 99. I replaced the sensor and everything was ok for about 3 days. Yesterday at a stop light the gauge started fluctuating again but not as wildly.... I turned on the heater to see if it had any effect but it didn't seem to. I turned onto the highway and it was fine the rest of the way home (no check engine light).
I had read about another guy with the same issue who found that a wire from the sensor in the harness was shorting out on the rear of the engine. I had not disconnected the battery when I replaced the sensor so I decided I would disconnect the battery, clean the terminals and test everything. Everything was good with the battery and alternator...left it disconnected for maybe 15 minutes. I saw that the main harness that goes to the PCM had a spot where it had rubbed through, but the affected wires did not appear to be the ones coming from the ECT. I zip tied it up off the contact point though.
Drove to my dad's and home last night (only about 7 min each way) and work this morning with no issues so far. I'm not confident since the only changes were 1. disconnected the battery and 2. lifting the harness up off of the contact point it was laying on. If this continues, any idea what I should be looking at next? Coolant was changed in 19 when radiator was replaced, reserve tank stays full, no obvious leaks anywhere and good heat with heater on.