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 MANUALSVOLVO2001S40 L4-1.9L TURBO VIN 29 B4204T3REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSCHECKING THE COMPRESSION
2001 Volvo S40 L4-1.9L Turbo VIN 29 B4204T3
Checking The Compression
2001 Volvo S40 L4-1.9L Turbo VIN 29 B4204T3SECTION Checking The Compression
Checking the engine:
Checking the engine:
- Ignition off
- Disconnect system relay 2/14
- Remove spark plugs.
Check the compression at wide open throttle (WOT).
In particular, check for uneven compression between the cylinders.
Note! Compression testing should always be carried out at wide open throttle (WOT) and with the engine at operating temperature. Diagnostic trouble codes (DTCs) ECM-24 and ECM-A3 will be stored because the system relay is disconnected.
Is the compression OK?
Yes - No Fault Found
No - Engine repairs
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Engine repairs
Carry out the repair required to the engine.
Continue - Verification
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Verification
Hint: Check after repair that the fault has been rectified.
- Reinstall system relay 2/14.
Start the engine and check that idle speed runs evenly.
Is idle speed even?
Yes - FAULT FOUND
No - No Fault Found 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 engine:
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.