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01 Flashing light then random codes after sparkplug install...


NAXJA Forum User
01 xj 233,000
I should have posted this week's ago when the car was in my possession and was fresh in my brain . I'm hoping it will spark some good conversation or when I post the fix (hopefully) help somebody else out... I had a flashing engine light that happened once and went away after restarting car. Naively I went out of town 3 weeks later with no issues and it happened again to not go away. It was basically running a little rough like in 5 cyclinders...Took it too a small towns mechanic and he said it was a #6 misfire .. tested the sparkplug no spark. Put a new spark plug in... now is where it gets strange ... absolutely no start and is throwing cps code that it didn't have before.
Dude ordered a new cps didn't change a thing. The thing under the cps was a little wobbly but I'm not sure if it was that bad or causing the issue... anyway it also randomly threw a 700 something something transmission code randomly at the end to throw even more confusion
I insisted maybe the pins were damaged from putting the coil pack on with the connector still connected but he checked it with a mirror and I'm hoping would test it some otherwise down the line :/
Any pending or current Check Engine Light trouble codes? What is missing, fuel or spark ?

The coil rail can be tested. With age and wear of all the XJ's, wire harness defects are common. Start with a look, wiggle, and poke test. Look at every wire harness and engine sensor for signs of chafed or melted wire insulation. Deteriorated insulation is common near the wire plugs. Wiggle and poke all the wires and wire connectors. Don't forget the O2 sensors.

Next level would be using your volts/ohms multi-meter to test continuity between each engine sensor and the PCM. Test grounds also.

Unfortunately, nobody can advise to measure 3.5 inches down the blue wire and that will be the problem.
I dont have the vehicle if its been this long and they havnt figured it out Im going to have to try to limp it somewhere I wonder what they are going to charge me for looking at it.... Apparently it was just the 6 misfire with no spark. changed the plug but then it wouldnt run at all strange. he tested for for power at the CPS what other sensors?.. didnt think of the o2 sensors
01 xj 233,000
Dude ordered a new cps didn't change a thing. The thing under the cps was a little wobbly but I'm not sure if it was that bad or causing the issue

I think we might be confusing the crankshaft position sensor on the bellhousing, and the camshaft sensor in the distributor. The magnet that triggers the sensor in the distributor has been known to break off and throw codes that aren't fixed by replacing the sensor.

While most people call the one on the crank/flywheel the CPS, the FSM calls it the CKPS and the distributor sensor the CPS.
Are you having a no start issue or rough and stalling? If it's a no start look at the tack when cranking. It should pop up a little bit ~300 rpm. If it doesn't the crank sensor or wiring would be suspect. It's possible the wiring was damaged and pulling the sparkplug moved wiring.
It was running rough til we switched the spark plug. then it was no start. then it randomly ran (decent?) and would die. i suggested he damaged the wiring when i did it years ago i found it much easier to remove clip lol... he insited the harness was fine because he looked at the back of the clip where the wires go in with a mirror
i suspect its the crank position sensor. that's on the bell housing. with out that sensor the ecu has no idea the engine is spinning. sometimes the wire will rest on the exhaust and melt. and moving the harness doing the spark plug may have moved it and shorted it out.

i have had mine melt so when on the highway it would bump the exhaust and short and it would kill the engine or cause misfires as it bounced off the exhaust.
Bad coil pack. Mechanic had it a month said sorry couldn't figure it out I thought it had some harness gremlin so I happily paid $125 for a cps and his time. Drive away its misfiring again.. mind you I'm from out of town. Drop it off at another mechanic. Leave town he calls me this morning your cars done it was a bad coil pack $288...unreal I would have been better off stranded at the parts store trying to figure this out