Why do ignition systems give technicians problems when diagnosing ignition-related misfires? The answer is that some technicians use tests that might give inconclusive results or do damage to the coil or drivers inside a module.
Diagnosing the problem comes down to understanding what causes a loss of fuel pressure.
For late-model vehicles, the norm is one ignition coil per cylinder, commonly known as coil on plug. The task of providing voltage potential to each spark plug is performed so reliably that it’s easy to take for granted.
Andrew Markel tackles the age-old diagnostic technique of hitting the starter with a hammer, and the obvious disadvantages to doing so on starters in modern vehicles. Sponsored by Denso.
Andrew Markel shows how to voltage drop test a starter when there is a slow crank, despite the battery and starter having enough voltage. Sponsored by Bosch Automotive Service Solutions.
This informational TSB applies to Audi vehicles with a start/stop system. The start/stop system allows automatic engine stops and starts. Although the driver expects it, the engine may not automatically be switched off due to many different factors.
Andrew Markel discusses service opportunities for vehicle stop-start systems and how several modules are involved in the activation of the feature. Sponsored by Bosch Automotive Service Solutions.
The most common diagnostic procedures for fuel pumps in the past were analog and hands on. Most fuel pump-related problems could be solved with a pressure gauge and voltmeter. Today, the scan tool is the most important tool when diagnosing a fuel supply problem.
The diversity of modern ignition coil designs has made ignition oscilloscope analysis more difficult because many ignition coil waveforms deviate from the conventional norm. Consequently, oscilloscope diagnosis shouldn’t be considered a definitive test of ignition coil condition unless it can be compared with a known-good waveform.
This month’s Diagnostic Dilemma concerns a 2003 Chevrolet Tahoe with a parasitic battery drain that leaves it with a dead battery. The first step in diagnosing a parasitic drain is interviewing the customer to determine the average number of days and the driving conditions under which the battery drains.
The PCM continuously monitors the commanded and actual throttle positions. The commanded throttle position is compared to the actual throttle position based on accelerator pedal position and possibly other limiting factors, and both values should be within a calibrated range of the other.
If you have just cleaned the throttle body and now you’ve a fluctuating idle and code P2279 (intake air system leak), the problem could be that the system needs to relearn the new throttle plate position because the system could be operating using the old data.