My XJR has been in the shop several times with a check engine issue that has never been resolved. My check engine light has been on since my last service and the dealership has tried to diagnose the problem for years now to no avail. I had to get my car smogged and of course it failed with the CEL on so I took it back in and after 4 days of trying everything they could they said it was a bad cell in my battery. They replaced the battery and reset the computer and i drove it home with no codes. The next morning I went to take to the smog station and the CEL came on again. They said it was the battery due to the fact it was producing random codes that when checked produced no problems. Has anyone had an issue like this and resolved it.

 

Should I assume that with all the dealer work they checked all the B+ and ground connections for corrosion and tightness?

What are the random codes? Could they all be CAN related?

 

They said they checked all connections. I am taking it back today I just don't know what else to tell them. The codes were for the ECM and something about the drivers seat and something to do with the transmission. When I drive it the transmission light comes on with the check engine light but if I shut it off and let it sit a minute the transmission light goes off but CEL stays on.

 

Get them to give you a specific list of the codes set. Once set, as by the transmission, the CEL will stay on and record a specific numeric code even after the original problem goes away.

One thought, ask them to check the connector at the rear of the transmission for corrosion/connection.

 

They told me today that a code for the transmission never came up but it coded the ECM which they replaced last year and the master seat control module which the tech said could be why the transmission light came on. They have already checked for corrosion at the connections and checked all the wiring that would be involved with the codes that come up. I explained to them today that we live in the mountains about 3000 elev. to which they said the cold may create more resistance in the line and the hills may put more strain on the transmission which may be why they could not replicate the problem. I don't know, does any of that make sense?

 

Bad throttle position switch could be causing both the engine and trans MIL's. Have somebody with Jag equipment pull the codes.

 

pull all the codes and see if they stay consistent. that should make it easier to find the real problem.