Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSVOLVO2004S80 L6-2.9L TURBO VIN 91 B6294TREPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONMANUFACTURER CODE CHARTSECM CODES (ENGINE CONTROL MODULE)ECM-801AFAULTY SIGNAL OR SIGNAL MISSING
2004 Volvo S80 L6-2.9L Turbo VIN 91 B6294T
Faulty Signal or Signal Missing
2004 Volvo S80 L6-2.9L Turbo VIN 91 B6294TSECTION Faulty Signal or Signal Missing
Faulty signal or signal missing
Checking the connectors and components
Check the battery voltage.
Check the charging function of the generator (GEN).
Check the fuse before the circuit. If the fuse is blown, check the circuit. Check for a short-circuit to ground.
Check the cable between system relay terminal #5 and control module terminal #A17 (#A17). Check for an open-circuit.
Check the engine control module (ECM) and system relay connectors. Check for contact resistance and oxidation.
Remedy as necessary.
Try a new system relay if no fault is found during the above fault-tracing.
Hint: Read off the voltage from the system relay to the engine control module (ECM).
Other information
- To fault-trace the charging system, see Fault-tracing and testing the voltage supply system Component Tests and General Diagnostics
- For further information about the fuses and relays, see the Wiring Diagram
- To connect the breakout box and access the control module, see Connecting the breakout box, B5254T2 Connecting the Test Box
- For information about signals on 5 cylinder engines, see Signal specification Signal Specification
- For information about signals on 6 cylinder engines, see Signal specification Signal Specification
- Checking wiring and terminals Checking Wiring And Terminals
Continue - Verification
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Verification
Verification
Hint: After carrying out the repair, check that the fault has been remedied.
- Ignition on
- Read off the voltage from the system relay to the engine control module (ECM).
The voltage must be approximately 12 V.
Is the voltage correct?
Yes - Verification completed
No - Fault-tracing information
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Fault-tracing information
Information
Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.
Do you want to exit fault-tracing?
Yes - Exit Fault-Tracing
No - Attempt New Test
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Attempt New Test - Checking the connectors and components
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RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.