Diagnostic trouble code (DTC) information

Condition

Fig 1: Identifying Camshaft Reset Valve

Courtesy of VOLVO CARS OF NORTH AMERICA.

Diagnostic trouble code (DTC) ECM-644A is stored in the engine control module (ECM) if the camshaft is not in the correct position. The engine control module (ECM) registers this as a fault as soon as the engine is started.

The engine control module (ECM) registers a fault and diagnostic trouble code (DTC) ECM-644A is stored in the engine control module (ECM) if the camshaft position (CMP) sensor flanker is not correct in relation to the engine speed (RPM) sensor.

The engine control module (ECM) registers a fault and diagnostic trouble code (DTC) ECM-644A is stored in the engine control module (ECM) if the camshaft does not rotate quickly enough in response to the control signal.

Substitute Value

the variable camshaft is disabled

Possible Source

Faulty position

camshaft belt has jumped out of place on the cogs
defective reset valve
mechanical fault in the Variable valve timing (VVT) unit

Faulty control

defective camshaft position (CMP) sensor

Control too slow

open-circuit in signal cable
open-circuit in power cable
contact resistance
short-circuit to ground in signal cable
short-circuit to supply voltage in the signal cable
low oil pressure
poor oil quality
defective reset valve
mechanical fault in the Variable valve timing (VVT) unit

Fault symptom[s]

poor performance