Diagnostic Trouble Code (DTC) Information ECM-821B

Condition 

Fig 1: Identifying Main Relay

Courtesy of VOLVO CARS CORPORATION

The engine control module (ECM) checks the power supply from the system relay.

The diagnostic trouble code (DTC) is stored if the engine control module (ECM) detects that the power supply from the system relay is lower than a certain value.

The diagnostic trouble code (DTC) can be diagnosed when the ignition is switched on.

Substitute Value 

• None.

Possible Source 

• Faulty charging system
• Contact resistance in the terminals
• Open-circuit in the signal cable for the system relay
• Damaged system relay.

Fault symptom[s] 

• The starter motor turns but the engine does not start.