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I’m a DIY beginner working on my 2005 C230K Coupe (M271, W203) with the Sport Package and the 722.6 transmission. 117k miles.
Problem: Intermittent no-crank, no-start. Been happening for 1.5 years. Was very occasional, but now more frequent. Currently it happens about 1 out of 5 times. All dash lights come on, but silence when turning the key. It usually fires up on the 2nd or 3rd try.
What I’ve checked/ruled out:
New battery (12.5V resting).
Swapped starter and horn relays. Same outcome.
Fuse 52 upgraded to 20A.
Historical code B1003 (Aux Water Pump) – I have since unplugged the pump and cleared the code.
Removed #8 fuse from rear SAM yesterday to disable the alarm system. I suspected it may be causing a drain on my battery. I did this yesterday.
EIS Diagnostic Data (Launch CReader): During a failure (holding the key in Position 3 for 5 seconds):
Terminal 50 (CAN): OFF
Output Circuit 50: OFF
TCM Diagnostic Data: Saw this while key in Position 2 before starting, and while running.
Selected Gear (Selector Lever): P
Actual Gear (TCM Live Data): N
Target Gear: 5
All these tests were done with the car stationary. The car console shows "P," but my scanner shows this mismatch (Selector = P, Actual = N). I suspect the car is "vetoing" the start because it doesn't think it's safely in Park. But at the moment, I’m very concerned to see this data from the TCM be so mismatched.
While the car was running, I also recorded the Live Data from the TCM - with my foot on the brake, I switched through the gears with the shift lever. The data from that was not reassuring. I’ll try and post that as a video.
Question: Is the TCM data scary? Does this point to a worn shifter linkage bushing or a failing conductor plate/range sensor? Or is this still looking like an EIS (Ignition Switch) internal failure?
Hi Everyone. I want to give an update on my original post here - in case it can help someone with the same problem: Intermittent no-crank, no start. I resolved the issue, and my car has been cranking\starting fine.
The problem was engine oil intrusion into the TCM, specifically the connector closest to the center console. Yes - engine oil. Not transmission fluid. I had multiple oil leaks and fixed them: valve cover, cam adjusters and vacuum pump. While replacing the transmission pilot bushing I noticed it was saturated with transmission fluid. So, I thought it a good idea to check for transmission fluid migration into the TCM. Checked the TCM and instead found engine oil! Cleaned the connector and port on the TCM with MAF cleaner a few times. Put it back together and the car starts fine ever since.
I didn't crack open the TCM case to clean the circuit board. Replacement cost would be high and require dealership. Didn't need to anyway, apparently.
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