Losing Focus

This looked like a simple diagnosis.

A 2005 Ford focus1.6TDCI with the MIL light on, and black smoke coming from the exhaust during hard acceleration.

First we performed a visual inspection and noticed a new Air mass meter(AMM). The test drive proved the customer was right, black smoke and poor vehicle performance.

Time to attach the code reader.

P1101 was the code stored. This relates to the air mass meter out of self test range.
possible causes for this code include;
Low Battery Voltage
AMM partially connected
AMM contaminated
Ground or power supply problems
AMM open circuit to ECU
AMM damaged
ECU damage

But as the component is new, and the customer will be less than pleased if the diagnosis is the same as a few months ago, and the light comes back on with the same symptoms. The pressure is now on. What is causing the AMM to under read, a classic cause and effect diagnostic problem. The previous garage has fixed the effect, and the problem has returned, we need to establish the cause.

This is where information can help, the diagnostic triangle consists of three elements, equipment, information and knowledge. All three are required to diagnose vehicles effectively.



We discovered that the problem can be caused by the crankcase breather pipe contaminating the AMM, and ford has modified the pipe to help prevent the problem returning. They also reprogram the ECU with larger performance parameters to prevent the MIL illuminating.


I checked the software number and the vehicle needed the software upgrades, along with the modified pipe. However the AMM was now contaminated, as it was still relatively new I cleaned it with brake cleaner and hoped for the best. On test drive the vehicle performed as it should, and there was no evidence of the black smoke. Satisfied we had found the cause, the car was returned to the customer.