Injector Circuit Malfunction - Cylinder 3
The PCM detected a malfunction in the fuel injector circuit for cylinder 3, meaning the injector is not functioning properly or the wiring/connector to it is faulty. This causes incomplete fuel delivery to that cylinder, resulting in misfires and rough engine operation.
What You Might Notice
- Engine misfire on cylinder 3
- Rough, jerky idle
- Poor acceleration and reduced power
- Check Engine Light (MIL) illuminated
- Possible fuel smell from exhaust
Most Common Causes
- 1
Faulty fuel injector
The injector itself has failed internally, preventing proper fuel spray or flow. This is the most common cause of P0203.
- 2
Open or broken wiring to injector
A break in the electrical harness leading to cylinder 3's injector prevents proper signal from reaching the injector coil.
- 3
Short in injector circuit wiring
A short to ground or power in the wiring causes the PCM to detect abnormal resistance or signal loss in the injector circuit.
- 4
Bad fuel injector connector or PCM fault
A loose, corroded, or damaged connector at the injector or a faulty PCM output driver can prevent proper injector operation.
How to Diagnose It
- 1
Check Faulty fuel injector — The injector itself has failed internally, preventing proper fuel spray or flow. This is the most common cause of P0203.
- 2
Check Open or broken wiring to injector — A break in the electrical harness leading to cylinder 3's injector prevents proper signal from reaching the injector coil.
- 3
Check Short in injector circuit wiring — A short to ground or power in the wiring causes the PCM to detect abnormal resistance or signal loss in the injector circuit.
- 4
Check Bad fuel injector connector or PCM fault — A loose, corroded, or damaged connector at the injector or a faulty PCM output driver can prevent proper injector operation.
How to Fix It
- 1
Replace fuel injector
Remove and replace the faulty injector on cylinder 3 with an OEM or quality aftermarket injector. Ensure proper seating and electrical connection.
- 2
Inspect and repair wiring harness
Check the wiring harness leading to cylinder 3's injector for breaks, corrosion, or damage. Repair or replace damaged sections and ensure secure connections.
- 3
Clean or replace injector connector
Inspect the connector at the fuel injector for corrosion, loose pins, or damage. Clean with electrical contact cleaner or replace the connector if damaged.
- 4
Test and replace PCM if necessary
If injector, wiring, and connectors test good, the PCM output driver may be faulty. Have the PCM tested by a professional or replaced if confirmed defective.
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