Last August my climate control started acting erratic. Regardless of temperature, vent, or blower setting the system would complete turn off and turn back on. Sometimes it would be off (no airflow, control panel above radio completed powered off) for literally no more than a second, sometimes a few minutes, and sometimes off for multiple drive cycles in a day. Ambient temperature or humidity didn’t seem to affect it either way. Then approximately three months ago a check engine light appeared, revealing a P1699 CAN link ECM / Climate Control Module code. The CEL would be on for a day or two, I’d clear it, and it would return in a couple of days. The problem became progressively worse, and for the last month I’d been experiencing a very random Air Suspension fault message with no change in ride height or drivability. I ran SDD to retrieve the suspension codes, and the print out is attached below. Although very uncommon, I suspected the climate control module for obvious reasons. However I was skeptical it wasn’t a much larger problem, as this car had the water ingress into the ECM issue about six years ago. I feared these network communication issues were delayed affects of corrosion slowly returning, despite the ECM being quickly and thoroughly dried when the event occurred, and no drivability issues being present afterwards. I’d convinced myself these sporadic symptoms were all related to the ECM, and had mentally prepared myself to start tearing things apart, chasing harnesses, and likely needing a new ECM. These thoughts were further compounded by the fact that I’ve been with a Jag dealer for almost a decade, pretty intimately involved with these cars, and couldn’t begin to estimate the number of X350s we’ve seen through our shop without seeing a climate control module failure being in anyone’s memory.

However, on a gamble, I spent $30 and sourced a used CCM, C2C21158, wers #2W9318D493AE from eBay. All the resources I could find said this module had to be programmed as new to the vehicle, but one night I decided to work the leads away from the old and plug the used unit in. It’s quite difficult to access, and is located just above the accelerator pedal on LHD cars.
Climate control functionality was instantly restored, and all network / air suspension codes disappeared. I can’t tell you all how relieved I was. The CCM had failed hard enough to take down several parts of the CAN network. I’m anxious to get the old one out and examine the circuit board(s) for any corrosion or burn marks.

Hopefully someday this will help someone chasing this same or a similar issue. Without a doubt, these beauties will throw you a curveball every now and then. Happy motoring, all.