Diagnostic Trouble Code (DTC) Information

Condition 

Fig 1: Identifying Camshaft Reset Valve (Continuous Variable Valve Timing (CVVT))

Courtesy of VOLVO CARS OF NORTH AMERICA.

When the engine coolant temperature (ECT) is above 80 °C and the engine has been running for more than 2 minutes check the engine control module (ECM) camshaft adaptation ACTUAL and DESIRED values. If these values deviate too much (approximately 10 crankshaft ° for longer than 15 seconds) during " even " driving the engine control module (ECM) interprets it as a fault and diagnostic trouble code (DTC) ECM-640A is stored.

Substitute Value 

• none

Possible Source 

Incorrect signal 

• camshaft belt has jumped out of place on the cogs
• low oil pressure / bad oil quality
• defective reset valve
• mechanical fault in the Variable valve timing (VVT) unit

Fault symptom[s] 

• uneven idle
• increased emissions