My faithful '04 XJ (110K miles) wouldn't start...totally "immobilized". I returned 4-5 hours later and it started fine! Took it to dealer-pulled DTC codes and there were several...some relating to the Transmission Control Modulebut many more relating to the CAN ECM network links to ABS, Climate Control, Traction Control, etc., etc., etc.

Dealer replaced MAP/Mass Air Flow meter (P0105), butsaid I probably also need a new transmission rotary switch (P0706,P1774, P1798, P1799, and P1797)...for $2300! I passed on this "suggestion".

But I'm skeptical that the real problem was solved; i.e., all those various CAN ECM network link failures.

Any ideas?

 

I'm not an expert, but why the engine would not start because of a transmission rotary switch?

I would even question the MAP replacement, it would still be able to run - poorly, but is has some "safe" defaults in the ECM in case of sensor failures.

All these sensor signals travel via electrical cables and if you have an issue with your CAN or other network it can causeall sorts of "fake" symptoms.

Check for watter in the trunk - near the fuze box and other cables. From other posts here this could cause all sorts of "odd" issues.

 

The rotary switch is part of the reporting sensors that tells the ECU the car is in a gear that it is allowed to start in. I doubt any of these things are a problem and I doubt your MAF was bad. Thereis a TSB out there for a bad connection in the CAN Bus system. It is very likely a loose or damaged connector only. I recommend to always get suspicious when you hear that you have multiple simultaneous faults, especially in expensive parts. Unless you just had a bad accident, this is very unlikely. If you know where the connectors for this system are, start pulling them apart and looking for problems. If you need more info, you will need to go to Alldata.com or one of the other information sources for detail of all this.

The car does have an MAP sensor, but it is used for EGR diagnsotic testing only, it does not input to the ECU for engine management. The car uses the MAF for mixture ratio development.