Complicated diagnosis issues… Will pay $20 for helpful advice!

[Justin Kasowski]

** HELP IS VERY APPRECIATED, WILL VENMO $20 TO WHOEVER HELPS ME DIAGNOSE THIS **

TLDR: 2008 Saturn Vue XE (2.4L Ecotec) – replaced camshaft actuators, camshaft position sensors, and crankshaft sensor… ECM isn’t sending the signal to spark or inject fuel, car cranks but doesn’t start. Tech-2 initially read codes for “Failure to connect to ECM”/”Crankshaft position sensor” after trying to start with a low battery. Attempted ot start with a fresh battery after clearing codes and no codes pop but the scanner “Failed to detect” body control module. Do I need to replace my BCM? Would a bad BCM be preventing the car from running? What are my next diagnosis steps?

Full story: Initially had codes for P0014 and P0010. Replaced camshaft actuator solenoids. Few weeks later, codes came back and car had intermittent starting problems. Thought I got a bad set of actuators since I ordered through Amazon. Decided to put off replacing them again. Drove maybe ~300 miles with those codes and the very occasional failure to start. Then one day, car dies on the highway.

At this point, I’m thinking ECM is acting up since the codes came back with new parts and now something is keeping the car from running. Car will crank with power but doesn’t run. Check for fuel, there’s pressure at the rail but spark plugs are bone dry if you pull them after attempting a start (indicating fuel pump is fine but injectors aren’t firing). At this point, there are no codes besides the P0010 that had come back on. I decided to replace the camshaft position sensors since these could stop the car from running and may also be a cause for P0010. No luck.

Hoping it was some weird computer issue, I disconnected the battery, let the car sit, reconnected. Codes are cleared, attempt to start and it still just cranks but doesn’t run. I do the starting fluid in throttle check for spark. Car doesn’t run implying no spark either. I pull the ECM out to get the part number, but wanted a better diagnosis before just replacing ECM. Someone on another forum suggested it might be crankshaft position sensor since that typically fails to send a code when it fails. Replaced it. Hooked the battery back up and attempted a start. Car cranked very weakly. Battery was dead from trying to start it ~50 times without ever charging it. It did pop some codes though. Failure to connect to ECM and Crankshaft position sensor. I clear the codes, hook in a good battery, and try to start. Same thing, cranks but doesn’t start. There is a check engine light, but no codes. It does have a “Failure to connect” to the car’s BCM. I’m not sure if trying to start the car with a low battery produced erroneous codes the first time. Multiple start attempts with a fresh battery only pop the “Failure to connect to BCM”.

I’m a bit lost on where to go from here. The car doesn’t display any symptoms of a bad BCM. Windows/locks/instrument panel all function correctly. It tells me when I have a door open, mileage reads fine, etc, etc. The only reason I could even think of for the BCM preventing the car from starting would be it doing something weird for anti-theft. The only weird symptom (which I’m not sure if it’s normal or not) is that I have to reset my HVAC system with the Tech-2 every time I disconnect the battery. BCM seems like a complicated procedure since it’s supposed to be set to your car’s VIN. Would like to know for sure what the issue is before just throwing more parts at it.

I ordered a new battery since I seem to have killed the old one. I’m going to let the car sit for ~48 hours with no battery and will try to start it again tomorrow. Hoping that works or someone in here knows where to go next. I don’t think bringing it to a “real mechanic” would be super beneficial as I feel like a pretty competent mechanic myself and this has me baffled.

Topic

[Sam Roodman]

Not sure if this will help, but its probably a step in the right direction:

[Author]

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