Volvo fault guide.

Search Volvo diagnostic trouble codes by number or symptom. Every entry explains the likely cause, the symptoms and where to start the repair.

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P0016
Powertrain

Crankshaft / camshaft position correlation

Likely causes: Timing belt or chain out of alignment; VVT actuator stuck; sensor fault.
Symptoms: Rough running, poor start, reduced power, MIL on.
P0087
Powertrain

Fuel rail pressure too low

Likely causes: Weak fuel pump, blocked filter, leaking regulator or injector.
Symptoms: Hard start, hesitation, limp mode under load.
P0234
Powertrain

Turbocharger overboost

Likely causes: Stuck wastegate or boost-control valve; sensor fault.
Symptoms: Power cut, limp mode, boost surge.
P0299
Powertrain

Turbocharger underboost

Likely causes: Boost leak, hose off, wastegate stuck open, weak turbo.
Symptoms: Sluggish acceleration, reduced power.
P0420
Powertrain

Catalyst efficiency below threshold

Likely causes: Aged catalyst, upstream/downstream sensor drift, exhaust leak.
Symptoms: MIL on, minor fuel-economy loss.
P2015
Powertrain

Intake manifold runner position sensor

Likely causes: Broken swirl-flap linkage or actuator; sensor fault.
Symptoms: MIL on, rough idle, minor power loss.
P0401
Powertrain

EGR flow insufficient

Likely causes: Clogged EGR passages or valve; cooler blocked.
Symptoms: MIL on, knock, higher NOx.
C0031
Chassis

Left front wheel-speed sensor

Likely causes: Damaged sensor or wiring, corroded tone ring.
Symptoms: ABS/traction light, no stability control.
C0561
Chassis

System disabled by another fault

Likely causes: A related chassis system has a stored fault blocking operation.
Symptoms: Multiple chassis warnings until root fault cleared.
C0040
Chassis

Right front wheel-speed sensor

Likely causes: Sensor gap, damaged wiring, debris on tone ring.
Symptoms: ABS light, uneven braking feel.
U0401
Network

Invalid data from ECM

Likely causes: CAN corruption, failing ECM, wiring or gateway fault.
Symptoms: Warning lights, feature loss, limp mode.
U0121
Network

Lost communication with ABS

Likely causes: Bus fault, connector, or failed ABS module.
Symptoms: ABS/stability lights, no wheel-speed data.
U0100
Network

Lost communication with ECM/PCM

Likely causes: Power/ground to ECM, CAN wiring, or ECM failure.
Symptoms: No-start, multiple warnings, no live data.
B1000
Body

Control module internal fault

Likely causes: Internal module failure or corrupted configuration.
Symptoms: Feature loss on the affected module.
B200A
Body

Restraint system fault

Likely causes: Seat-belt, airbag circuit, crash sensor or clock-spring.
Symptoms: SRS/airbag light on, safety function impaired.
P1614
Powertrain

Immobiliser / key authentication

Likely causes: Key not recognised, immobiliser data mismatch, antenna fault.
Symptoms: No-start, security light, engine cuts.
This guide is a starting point for diagnosis. Always confirm with live data and the vehicle's own stored fault information before replacing parts. Open a session in VCTS Cloud to read the car directly.

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