What causes fault code P029C?

• Most likely: Faulty fuel injector for cylinder 1 (internal mechanical leak or debris) • Likely: Wiring or connector issue (short to ground on the control circuit) • Possible: Contaminated fuel causing deposits within the injector nozzle • Rare: Faulty fuel pressure regulator or damaged ECU injector driver

Powertrain (Engine & Gearbox)Standard EOBD

P029C - Cylinder 1 – Fuel Injector Leaking

Q: What are the symptoms of fault code P029C?

• Check Engine Light (MIL) illuminated • Rough idling and engine misfires • Increased fuel consumption • Black smoke from the exhaust during acceleration • Strong smell of unburnt fuel • Hard starting (especially when warm due to flooding)

Q: How do you fix fault code P029C?

STEP 1: Inspect the connector for injector 1 for corrosion or physical damage. STEP 2: Perform a fuel pressure leak-down test. If pressure drops rapidly after the engine is turned off, a leak is present. STEP 3: Measure injector resistance (typical range 11-16 Ohms). Use an oscilloscope to check the injector signal; a constant ground signal indicates a short in the wiring. STEP 4: Swap injector 1 with injector 2. If the fault code follows the injector (e.g., to P029E), the injector is faulty. STEP 5: Replace the injector and reset fuel adaptations using a scan tool.

Last updated:1 February 2026

Related:Fuel Injector, Engine Control Unit (ECU), Fuel Pressure Sensor, Oxygen Sensor (O2), Wiring

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0200

Injector Circuit Malfunction

P0201

Cylinder 1 Injector Circuit Open

P0202

Injector Circuit - Cylinder 2 - Malfunction

P0203

Injector Circuit - Cylinder 3

Technical Description

P029C is a diagnostic trouble code (DTC) that indicates the Engine Control Unit (ECU) has detected a leaking fuel injector for Cylinder 1. The ECU monitors fuel trim values and oxygen sensor feedback to determine if a specific cylinder is running too rich. If the injector fails to close completely or has a compromised internal seal, it will allow excess fuel into the combustion chamber, causing a rich condition that the ECU cannot compensate for through standard pulse-width modulation.

Possible Causes

Faulty fuel injector for cylinder 1 (internal mechanical leak or debris)

Wiring or connector issue (short to ground on the control circuit)

Contaminated fuel causing deposits within the injector nozzle

Faulty fuel pressure regulator or damaged ECU injector driver

Symptoms

Check Engine Light (MIL) illuminated

Rough idling and engine misfires

Increased fuel consumption

Black smoke from the exhaust during acceleration

Strong smell of unburnt fuel

Hard starting (especially when warm due to flooding)

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P029C - Cylinder 1 – Fuel Injector Leaking

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P029C - Cylinder 1 – Fuel Injector Leaking

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