Asian Systems Are Inter-Connected

Posted 3/11/2010
By Todd Erickson, AAM

We know that the newer the car, the more inter-connected its systems are. And we also know that often the customer's complaint doesn't match the problem.

Just the other day, I answered a hotline call on a 2005 Subaru Outback. The customer's complaint was that the cruise control lamp was flashing.

When the technician asked me how to diagnose the cruise control system, I asked him, "What engine codes do you have?" He told me that there was a code for an air fuel ratio sensor heater circuit and that he had a part coming in later that afternoon. Then he asked, "What does that have to do with the cruise control light?"

It just so happens that on a Subaru with a fly-by-wire throttle body control, the engine control module doesn't allow the cruise control to operate if there are any stored trouble codes in the engine control system. And if there are codes, the cruise control light starts to flash. It amazes me how many car owners give priority to the blinking cruise control lamp over the "Check Engine" lamp that is on steady.

I took another call on a 2006 Nissan Pathfinder. The customer complained that the transmission would start out in third gear. There were no codes in the transmission control module and no pattern to the failure. After the third call, I asked the technician if there were any codes in any other systems. It turned out there was an engine control system code P0340 for the camshaft position sensor. Once again, the part was on order and while the technician waited for it to come in, he decided to diagnose the transmission complaint.

After some research, I discovered that the transmission will go into a "fail-safe mode" on Nissan vehicles for any revolution sensor code such as a camshaft or crankshaft position sensor. After the P0340 code was fixed, there were no further problems with the transmission.

Keep these examples in mind the next time you have more than one system malfunction on the same vehicle at the same time.

Todd Erickson, AAM, is an Identifix Asian specialist. He is a certified Subaru senior master and ASE master. He has certifications in L1, L2, alternative fuels and medium/heavy duty truck.

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