Fix P0204: Mechanic’s solutions that WORKED

The P0204: Injector Circuit/Open – Cylinder 4 code signifies an issue in the fuel injector circuit for cylinder 4. It can result from a malfunctioning fuel injector, wiring problems, poor connections, or even an ECM driver problem. This code affects the engine’s performance and should be resolved to prevent misfires and maintain fuel efficiency.

P0204 quick overview

Meaning	P0204: Injector Circuit/Open – Cylinder 4
Is it serious?	This code can affect the engine’s performance and fuel efficiency. While not an immediate breakdown concern, it should be addressed to prevent engine misfires and potential damage.
Possible causes	– Faulty fuel injector in cylinder 4 – Wiring issues in the injector circuit – Poor connection or corrosion in the injector harness – ECM (Engine Control Module) driver malfunction
How to diagnose?	Injector Inspection: Check the condition of the fuel injector in cylinder 4 for any signs of damage or clogging. Wiring Examination: Inspect the wiring in the injector circuit for breaks, shorts, or damage. Harness Inspection: Check the injector harness for poor connections or corrosion. Test Injector: Use a noid light or equivalent tool to verify if the ECM is sending signals to the injector in cylinder 4. Swap Injectors: Consider swapping the injector in cylinder 4 with one from a different cylinder to see if the fault code follows. ECM Evaluation: If all else checks out, consider that the ECM driver for cylinder 4 may be malfunctioning.

How to fix P0204 – learn from mechanics

I looked into P0204 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: BMW

Vehicle Information: 1997 BMW 740iL 4.4L

Issue + Repair History:

• Car cranks but does not start.
• Strong spark at multiple coils.
• Fuel pressure at 45 psi key on.
• No injector pulse.
• OBD codes indicate injector circuit failure on all injectors.
• Tachometer and scan tool read 0 RPM while cranking.

Computer Codes & Descriptions:

• P0201: Injector #1 malfunction
• P0202: Injector #2
• P0203: Injector #3
• P0204: Injector #4
• P0205: Injector #5
• P0206: Injector #6

Suggestions to Fix Issue:

• Check ignition switch as injectors are powered via the switch.
• Diagnose the crank angle sensor.
• Inspect the wiring harness for chafing, particularly where it drops to the engine.
• Check the anti-theft system and reset if necessary.
• Examine the RPM sensor during cranking with a scope for weaknesses or non-existent signal.

Final Fix:

• Found the F2 fuse blown in the under-hood fuse panel (injector voltage).
• Located a bus bar style connector under the intake manifold with 14 wire connections.
• Joined the two sets of 7 wires together.
• Issue resolved by fixing broken wires in the left front fender from a previous accident.

Case #2: Ford

Vehicle Information: 2004 Ford Focus ZTS 2.0L

Issue + Repair History:

• Intermittent misfire with codes P0304 (#4 misfire) and P0204 (#4 injector).
• Also had an O2 sensor biased rich code.
• Good spark, fuel pressure, and leakdown tests.
• Swapping injectors didn’t resolve the #4 misfire.
• PCM replacement planned but not initially logical as P0204 code didn’t reappear, only P0304.
• Ignition system checked with known good parts.

Computer Codes & Descriptions:

• P0304: #4 Misfire.
• P0204: #4 Injector.

Other Test Results:

• Fuel pressure: within specs.
• Leakdown: within specs.
• Spark: within specs.
• Timing: within specs.

Suggestions to Fix Issue:

• Check the PCM warranty and programming requirements.
• Scope the injector drive signal from the PCM.
• Inspect the ignition secondary and primary, and current ramp on #4 injector circuit.
• Consider potential wiring issues or valve problems.
• Use a noid light to check if the computer is pulsing the injector.

Final Fix:

• Used a Rotunda VMM (scope) to examine the injector driver signal.
• Found the signal erratic with an unusually long ‘on’ time.
• Replaced the PCM, which resolved the issue with no problems

Case #3: Kia

Vehicle Information: 2003 Kia Sorento LX 3.5L

Issue + Repair History:

• Towed in with no power and service engine light on.
• Found codes P0700, P0304, P0204.
• Followed Mitchell’s flowchart for P0204 and replaced #4 injector but issue persisted.
• Swapped coils and plugs on that bank.
• Scanner data showed unusual fuel trim numbers for each bank.

Computer Codes & Descriptions:

• P0700: Transmission code.
• P0304: Cylinder 4 misfire.
• P0204: Injector circuit.

Suggestions to Fix Issue:

• Conduct a smoke test for vacuum leaks.
• Scope injectors to check for bad driver in PCM.
• Check for EGR issues near the cylinder.
• Use a noid light to test coil operation.
• Perform an engine compression test.
• Inspect the large connector on top of the manifold for issues with the injector connector.

Final Fix:

• Discovered loss of drive for injector 4 from the ECM.
• Replaced ECM with a used one, which solved the problem.

Case #4: Volkswagen

Vehicle Information: 2010 Volkswagen Jetta TDI 2.0L

Issue + Repair History:

• Car towed in with code P0204 (injector 4 circuit malfunction).
• Replaced injector #4, car operated fine for 5km, then went into limp mode.
• New code P0606 (internal control module processor fault) appeared.
• Erased code and test drove, but P0204 for injector #4 returned.

Related Repair History:

• Replaced #4 injector.

Computer Codes & Descriptions:

• P0204: Injector #4 N33 circuit malfunction.
• P0606: Internal control module processor fault.

Suggestions to Fix Issue:

• Program the injector to the ECM.
• Confirm the correct VW injector is used and check wiring to the injector.
• Swap injector #4 with another and see if the code follows.
• Ensure the new ECM is properly programmed/configured.
• Verify warranty coverage for PCM.
• Check the integrity of all supply and ground circuits, the charging system, and battery condition.

Final Fix:

• Found a bulletin indicating the need to replace all injectors, wiring harness, and flash ECU.
• Customer had insurance and took the car back to the dealer where insurance covered it.

Case #5: Dodge

Vehicle Information: 2002 Dodge Grand Caravan Sport 3.3L

Issue + Repair History:

• Engine starts and runs with an obvious cylinder misfire.
• Codes P0204 (injector circuit malfunction) and P0304 stored.
• Noid light testing on injector harness showed no signal for cylinder #4.
• Tests on wires and injectors were within specifications.
• Suspected #4 driver in ECM is not working.

Related Repair History:

• Injector #4 has been replaced with a dealer part.

Computer Codes & Descriptions:

• P0204: Open circuit #4 cylinder.

Other Test Results:

• Resistance from #4 injector to ASD relay: OK.
• Resistance on brn/tan wire from #4 injector to ECM: Same as other injectors.
• Swapped #4 injector with #2 injector: Code still P0204 for cylinder #4.
• Checked for bad ground with ASD relay jumpered: OK.

Suggestions to Fix Issue:

• Back probe cylinder #4 injector at PCM.
• Check for power at the #4 injector power wire.
• Check wiring harness for shorts, especially near the coil pack.
• Consider PCM replacement if wiring checks out.
• Consider potential shorts to ground in wiring.
• Examine key for programming needs if replacing PCM.

Final Fix:

• Found melted wire insulation on 5 wires in injector harness behind coil.
• Repaired all wiring and checked over to the computer.
• Found no pulse from the computer back to injector #4.
• Replaced computer, resolving the issue.

Advice	Diagnostic Step Description
Check injector harness for wiring issues	Physically inspect the injector harness for damaged wiring, especially near the coil pack.
Verify power at the injector	Use a test light to check for power at the injector’s power wire to ensure it’s not compromised.
Back probe the injector at the PCM	Use back probing to determine if the problem lies in the wiring harness or the PCM by checking for signals at the PCM connector.
Consider PCM replacement if wiring checks out	If the wiring harness tests fine, consider replacing the PCM (Engine Control Module) as it might be the issue.
Check key for programming needs if replacing PCM	Verify the type of key (black or gray) and determine if key programming is required when replacing the PCM.