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2003 Dodge Grand Caravan 3.8L P0203 Fuel Injector Code: Diagnosis and Repair Steps

Model: 2003 Grand Caravan Fault Code: P0203 Posted: 2016-02-21 12:00

My 2003 Dodge Grand Caravan with a 3.8L engine is showing Diagnostic Trouble Code (DTC) P0203, indicating a fuel injector circuit fault on cylinder #3. I initially replaced all six fuel injectors to resolve the issue, but after clearing the code, it returned immediately. Further investigation revealed that the fuel management wiring harness was severely damaged due to poor manufacturer installation — the wires were fused and shorted together. I replaced the entire fuel injector wiring harness with a new one, ensuring all connections are secure and free of corrosion. After re-clearing the codes and starting the engine, the P0203 code reappeared. At this point, I suspect either a faulty Powertrain Control Module (PCM) or an issue in the signal circuit between the injectors and the PCM. I’ve tested the injector circuits using a multimeter and a noid light: when testing cylinder #3 (rear bank, center position), no 12V is detected at the injector terminal during key-on engine-off (KOEO) conditions. The noid light shows no signal on #3, while all other cylinders respond normally. This suggests that either the injector itself or its wiring to the PCM may be faulty. I’m now considering whether the PCM has been damaged due to the original harness failure and am seeking guidance on how to proceed — including whether a new PCM is required, or if further diagnostics (such as measuring resistance between injectors and PCM) are needed before replacing components.

Related fault codes

P0203

Comments (10)

Anonymous 2016-02-21 12:31

Using a noid light on cylinder #3 — is it flashing, steady, or not at all? Is there 12V present at the injector terminal? Ensure the connector is fully seated and free of corrosion. Confirm we're aligned: where exactly is cylinder #3 located in the engine?

Anonymous 2016-02-21 15:36

On a 3.8L Dodge engine, cylinder #3 is typically located on the rear bank, center position (on the side of the front-wheel-drive engine). However, since I replaced all six injectors and installed a brand-new fuel management harness with full wiring to each injector, the issue likely lies at the PCM level — unless there's another fault in the signal path between injectors and the PCM.

Anonymous 2016-02-21 15:44

Kev2: Is a noid light available for rent at places like O'Reilly Auto? It works by plugging into the injector harness instead of connecting to the injector. Would using a noid light allow me to detect signals sent from the PCM — thus eliminating the need to buy a digital multimeter (DVOM) to check the PCM directly? Is that correct?

Anonymous 2016-02-22 16:09

Cylinder #3 is in the rear bank, center position. A noid light simply plugs into the injector harness and should flash during cranking or engine operation. The fuel injector circuit receives 12V from the ASD relay for all six injectors; a separate signal wire runs to the PCM for each cylinder. This signal wire is grounded when commanded by the PCM, causing the injector to spray fuel. The PCM monitors voltage on this wire — typically dropping from 12V to near 0V during injection.

Anonymous 2016-02-23 18:55

Thanks, Kev2! I correctly identified cylinder #3, but as I mentioned, I replaced all six injectors and installed a new wiring harness with full connections. A mechanic advised me that without a noid light, it's hard to test — he suggested renting one or buying online. After inspecting the original harness, he noted that the wires were severely melted and fused together, concluding that the PCM may be damaged due to this failure. I’m now looking for a used PCM unit to install and reprogram.

Anonymous 2016-08-10 23:57

This message is for Kev2 — I’ve been reading your post in response to dean64a. I have code P0204, but when I tested cylinder #3 with a noid light, it showed no signal. All other cylinders work fine. Like dean, I replaced the harness with a new one and now suspect either the PCM or the wiring between injectors and the PCM. Any advice would be appreciated. Thanks, Joe.

Anonymous 2016-08-11 08:09

When an injector is unplugged — do you have 12V at the injector terminal? If yes, check the signal wire from the injector to the PCM. This wire should not have voltage when idle; it should be grounded only when commanded by the PCM. Measure resistance between the injector and the PCM. Also note: front cylinders are #2, #4, #6 — could you be confusing cylinder #3 with #4? Cylinder #4 is located at the front center position.

Anonymous 2016-08-11 20:43

I unplugged injectors #3 and #4 (including #3) and tested with a voltmeter. Key off, negative connected to battery negative, positive applied to both sides of the injector harness. No 12V reading — instead, I measured -0.02 volts on one side. Could this indicate a test error or a faulty connection?

Anonymous 2016-08-12 10:05

KOEO (Key On, Engine Off): is there 12V present at the injector terminal? Yes or no?

Anonymous 2016-08-12 14:14

I cannot get 12V from either injector wire under KOEO conditions. The noid light test confirms that cylinder #3 (rear middle) shows no signal — all other cylinders flash normally.