Hello! I recently purchased a 2011 L322 (LHD). I has started throwing a code, C1A08-1C, indicating that the supply voltage to the pressure sensor is out of range. When I read the live data with IID tool, it shows 0.980V. Using a volt meter, I read 5V at the connector, both while plugged into the sensor and while unplugged from the sensor.

I assumed that supply voltage must be measured in the module and thought that the module must have an internal issue, so I bought a used module and swapped it out... but it gives the same result.

The pressure sensor will report higher voltages, ie I've seen 2+V from it, which aligns with me actually reading 5V at the connector.

I'm at a loss as to what/where the issue could be. The wiring is utterly simple back there, and a very short run between the switch and module, and it all measures correctly as best as I can tell. The module is connected to the rest of the system via the CAN bus, which... if there was a physical issue there, I'd expect a lot more problems?

Would love any insights that you might have. Thanks!

This morning, I decided to try and simply the circuit, so to speak. I started by disconnecting the height sensors, which are the other sensors receiving a 5V signal. No change with them disconnected. Of course, if there was a short there, maybe that isn't surprising.

Next, I pulled the module out from behind the fuseblock so that I could more easily test things. I started by pulling the small connector that contains the wiring to the pressure switch. Interestingly, even with the plug disconnected, the ECU reports .980V to it; I'm not very good with electricity, but this makes no sense to me... doesn't there have to be some resistance/ground for a current to be present?

I tried my "new, used" module again, and get the same result. I also pulled the "large, middle" plug to the ECU, no change. I couldn't pull the outer two plugs without the module shutting down.

At this point, I am out of ideas. I feel like it must be something relatively simple, but... I have no idea what.

Check for corroded fuses, I've had more than a few issues with EAS due to this. Open circuit voltages can be misleading as the control module will recognise something is disconnected, get a decent set of backprobe pins and an accurate voltmeter.

I'll take a look. But every other signal, function coming from the EAS module is working fine. Everything I measure says that this circuit is fine, too. I've checked continuity of the wires, checked them for shorts/grounds, etc. Everything is nominal according to my measurements. I've added jumper wires to ground, for the 5V line, etc. I've unplugged the connector from the ECU, it still reads .980V. I grounded the 5V line from the ECU and it did move, to 0.990V. I'm stumped.

Edit: I should also point out that when I clear codes, until the ECU runs its check, the car functions normally. I haven't figured out what triggers the code. Sometimes it seems immediate, other times it's a day.