2003 Dodge Durango P0201 Fuel Injector Code: Diagnosis and Fix for Rough Idle and Misfire

Hi everyone, I'm troubleshooting my 2003 Dodge Durango SLT 4x4 with a 5.9L 'Z' engine (360/5.9). Recently acquired for around $1,100, the car has developed several issues after pickup. Symptoms: - Rough idle - Loss of power during acceleration - Misfire sensation similar to a rich cut — though no misfire codes appear in the system Background: At purchase, I discovered the fuel tank was empty. This likely led to contamination in the injectors, so I've scheduled an injector overhaul using a kit with new O-rings and basket filters (designed for 4.7L injectors — but compatible based on fitment). I also replaced the water pump and viscous fan, flushed the cooling system, and added fresh antifreeze. Upon arrival home via recovery truck, I found all spark plugs were cold-fouled, with five significantly worse than others. Upon inspection, four of the eight secondary ignition wires were incorrectly routed on the distributor — a known issue documented in TSBs. I re-routed them correctly and installed new RC12LYC plugs (gapped at 0.040"; LC4s unavailable locally). The projected ends are about 3mm longer, which may slightly advance timing — but I'm hopeful this resolves some pinging. Additionally, the distributor clamp bolt was extremely loose, allowing movement under engine vibration. While modern distributors don't adjust timing like older models, I believe the PCM requires a stable position to effectively manage ignition timing. After tightening it securely (hand-tightened until no further movement), initial starts were difficult. Rotating the distributor about 10 degrees clockwise improved starting significantly. The misrouted wires explained four of the severely fouled plugs — but plug #8 remained untouched for over 11 years and appeared original. I used a two-foot torque wrench with penetrating oil to remove it. After installing new plugs, performance improved noticeably — yet a check engine light activated with a P0201 DTC (Fuel Injector Circuit Malfunction). Key questions: 1. Does a blocked fuel injector trigger a P0201 code? Or is this code strictly related to electrical circuit conditions? 2. Could a different injector be responsible for the P0201 code? The wiring harness is clearly labeled, and cylinder 1 is correctly identified — but I will verify all injector resistances (all show ~15 ohms) and use an audio stethoscope to confirm firing patterns. I suspect a ground leak or electrical short in the injector circuit — possibly between the injector and PCM, or from the ASD module. However, the injectors appear to be firing audibly (tic-tic-tic-tic), and resistance readings are within range. Additional observations: - Both upstream and downstream O2 sensors cycle normally with good data. BlueDriver suggests this may resolve P0201 issues — is there any truth to this? - Small amounts of porcelain-like material were observed in the exhaust, indicating potential catalytic converter damage from prolonged operation on 3–4 cylinders. - I will perform a pressure test at the upstream O2 sensor (max 3 PSI); higher than that requires pipe testing. The engine runs quieter than other 2003 Durangos — which raises suspicion of internal issues. I also noticed a brittle, partially missing PCV grommet (12 o'clock to 1 o'clock), with occasional 'pink' sounds from the left valve cover area — likely related to oil leaks. A new PCV and grommet are now in hand (DHL from Germany). Manifold vacuum at idle is ~18 inches Hg — within normal range, no visible vacuum leaks. I'm considering TPS, IAC, or camshaft sensor issues — but I prefer simple fixes first. I have the service manual and Haines repair guide. Any input, confirmation, or counterpoints would be greatly appreciated! PICS: - Spark plugs laid out as viewed from over the radiator (cylinder 1 at bottom right, cylinder 8 at top left) — layout follows firing order: 1-8-4-3-6-5-7-2 https://www.dropbox.com/s/uuhy3hhl1ycp27s/plugs.jpg - BlueDriver freeze frame from code trigger (binary-like dump) https://www.dropbox.com/s/suiq6j0bv6k98...Driver.png I'm hoping this isn't a PCM issue — any missing pieces? Note: The P0201 code is specific to cylinder 1, though all injectors are firing audibly and resistance readings are normal. UPDATE (from user): After removing and inspecting the TPS, I found one wire was slightly crimped. I manually straightened it using a paper staple as a temporary probe for terminal access. The voltage reading was ~4.9V — within acceptable range. The potentiometer rotation appeared normal. I reinstalled the TPS and confirmed signal output via back-probing (center wire, terminals 1 & 3). The signal ranges from 0 to 5V as throttle position changes — consistent with expected behavior. While there's a slight lag between diagnostic tool and PCM, I plan to log data over time. Result: P0201 code cleared and has not returned since. I've ordered a replacement TPS (simple, inexpensive fix). If it takes more than two minutes to replace — you're doing something wrong! Next step: Test exhaust back pressure at the upstream O2 sensor. Suspect catalytic converter restriction is likely causing poor airflow and plug fouling. Any feedback or additional insights welcome!