BMW Cars 1999-06

Diagnosis & Testing


The distributorless ignition system can be diagnosed and tested using a logical test sequence. The system can be broken down into three basic components. These components are the inputs (sensors), the processor (Powertrain Control Module) and the output components (ignition coils). Basic troubleshooting of the ignition system can be accomplished by testing the input and output components. These simple troubleshooting procedures can be used to help locate and diagnose most problems.

Diagnosing the PCM using basic tools and test equipment requires a process of elimination technique.

  1. Check the operation of all input sensors. Please refer to Section 4 for additional information.
  3. Check the wiring for all input sensors for continuity or a short to ground.
  5. Check the ignition coils. Please refer to the following Ignition Coil Pack procedures for additional information.
  7. Check the ignition coil wiring for continuity or a short to ground.
  9. If the sensor inputs and the ignition coils are within specification, and the wiring is connected and functioning properly, the PCM could be faulty.

The Powertrain Control Module (PCM) has a fault memory to monitor the operation of the system. The PCM has the ability to recognize a problem in the system, and can prioritize the problem. If the problem is severe enough, the Malfunction Indicator Light (MIL) can be turned on by the PCM to indicate the problem is compromising the efficient and optimal operation of the engine. This test equipment is used to read the stored faults, as well as erase the faults from the PCM memory once a repair is completed.