Diagnostic trouble code (DTC) information
WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Condition
If the engine control module (ECM) does not receive a signal from the engine speed (RPM) sensor (signal missing), or if the control module counts more than two teeth too many or too few on the flywheel during one revolution (faulty signal): The control module interprets it as a fault and diagnostic trouble code (DTC) ECM-78 is stored.
Substitute Value
- No camshaft diagnostics
- No camshaft control
- Ignition retardation
- No boost pressure diagnostics
- No heated oxygen sensor (HO2S) diagnostics.
Possible Source
Signal missing:
- Open-circuit in the signal cable
- Short-circuit to ground in the signal cable
- Short-circuit to supply voltage in the signal cable
- Faulty engine speed (RPM) sensor.
Faulty signal:
- Loose connections
- Damaged flywheel
- Faulty engine speed (RPM) sensor.
Fault symptom[s]
- Malfunction indicator lamp (MIL) lit.