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2005 Dodge Ram 5.7 HEMI Misfire: P0301 and P0203 Fault Codes - Diagnosis and Fixes

Model: 2005 Dodge Ram 5.7 hemi Fault Code: P0203 Posted: 2010-02-11 12:18

Help needed! My 2005 Dodge Ram 5.7L HEMI engine is running roughly and shows fault codes P0301 (cylinder 1 misfire) and P0203 (injector issue on cylinder 3). I've already replaced the spark plugs and coil pack for cylinder 1, but the misfire persists. The P0203 code appears specifically on cylinder 3. Any suggestions on how to diagnose or fix this? Is it a faulty injector, wiring harness problem, or something else?

Related fault codes
P0203P0301
Comments (3)
Anonymous 2010-02-11 16:49

Use a noid light connected to the injector connector on cylinder #3 to check for proper signal. If the light flickers rapidly and brightly, it indicates an active injection signal—try swapping that injector with another cylinder. If the P0200 code disappears after the swap, the original injector is faulty. If the code remains, inspect the wiring harness near the A/C receiver/dryer for fraying or damage. This issue is well-documented in Dodge truck forums and often stems from worn or damaged wiring.

Anonymous 2010-02-11 20:15

Thanks for the tip! Would this fix resolve the misfire on cylinder #1, or does it only address the P0203 code on cylinder #3?

Anonymous 2010-02-12 06:03

If a wiring harness issue is suspected, don't overlook potential broken valve springs—especially common in older 5.7L HEMI engines. A damaged valve spring can cause misfires and erratic engine performance, even after replacing plugs and coils.