What causes fault code P028A?

• Most likely: Short to voltage in the injector wiring harness • Likely: Faulty fuel injector (internal electrical short) • Possible: Corroded or moisture-compromised connector • Rare: Internal Engine Control Unit (ECU) failure

Powertrain (Engine & Gearbox)Standard EOBD

P028A - Cylinder 9 Fuel Injector Control Circuit High

Q: What are the symptoms of fault code P028A?

• Check engine light (MIL) illuminated • Engine misfire on cylinder 9 • Reduced engine power (Limp mode) • Poor fuel economy or smell of raw fuel • Increased tailpipe emissions

Q: How do you fix fault code P028A?

STEP 1: Visually inspect the wiring to injector #9 for chafing, heat damage, or shorts. STEP 2: Measure voltage at the injector connector. With ignition ON, one pin should show battery voltage. Check the control wire; if it is shorted to power, trace the wire. STEP 3: Test injector resistance using a multimeter (standard specs usually 10-16 Ohms). Ensure there is no continuity between the pins and the injector body. STEP 4: Use an oscilloscope to verify the injector pulse-width signal. If the driver stays high constantly, the ECU driver might be damaged or the harness is pinched against a live wire. STEP 5: Replace the injector or repair the wiring harness as necessary.

Last updated:1 February 2026

Related:Fuel Injector Cylinder 9, Engine Control Unit (ECU), Wiring, Fuel Injection System Fuse

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

The P028A diagnostic trouble code (DTC) is set when the Engine Control Unit (ECU) detects a voltage on the fuel injector control circuit for cylinder 9 that is higher than the expected threshold. This typically signifies a short circuit to voltage (VCC) within the wiring harness or an internal short in the injector solenoid. Injector drivers normally pull the circuit to ground to activate; if the ECU senses high voltage during an 'on' command state, it triggers this code. This code is specific to engines with 9 or more cylinders (V10, V12, etc.).

Possible Causes

Short to voltage in the injector wiring harness

Faulty fuel injector (internal electrical short)

Corroded or moisture-compromised connector

Internal Engine Control Unit (ECU) failure

Symptoms

Check engine light (MIL) illuminated

Engine misfire on cylinder 9

Reduced engine power (Limp mode)

Poor fuel economy or smell of raw fuel

Increased tailpipe emissions

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P028A - Cylinder 9 Fuel Injector Control Circuit High

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P028A - Cylinder 9 Fuel Injector Control Circuit High

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