← Back to list

1998 Plymouth Voyager P0204 Code: Diagnosis and Solutions for Injector Signal Fault

Model: 1998 plymouth voyager Fault Code: P0204 Posted: 2016-06-10 10:06

I performed an injector click test and heard all injectors clicking normally. When I disconnected the injector wires while the engine was running, RPM dropped significantly; reconnecting them restored engine speed. The vehicle runs very roughly under load. I also tested the spark plug wires with the same result—no difference in performance. This is a 3.3L 6-cylinder engine that starts reliably every time and continues to drive, but the rough idle and poor responsiveness are concerning. The OBD2 code P0204 has been detected. I'm seeking advice on how to properly diagnose this issue. Possible causes include fuel pressure drop, vacuum leaks, or faulty injector wiring. I've checked the spark plugs—some appear black and wet, others dry and tan—which may indicate incomplete combustion. Key points to investigate: - Ensure all injector connectors are tight, free of corrosion. - Perform an ohm test on each injector to verify functionality. - Check for open or grounded signal wires in the injector harness—this is especially relevant for 1998 Plymouth Voyagers due to known wiring issues. - Conduct a fuel pressure test under KOEO (Key On, Engine Off) conditions and monitor for pressure drop over five minutes. - Consider adding a fuel treatment like SeaFoam or Techron to improve combustion efficiency. The signal wire from injector #4 is critical—when the PCM wants the injector to spray, it grounds the signal wire. The P0204 code indicates that the PCM did not detect expected voltage on this wire. I've measured 9 volts at the front injectors (including #4), which appears slightly low but consistent across all injectors. I need confirmation whether 9V is within acceptable range for a 3.3L engine and if there's a known threshold for signal voltage at the PCM terminal.

Related fault codes
P0204
Comments (4)
Anonymous 2016-06-10 10:46

Have you used an OBD2 scanner? The vehicle runs rough but only shows one code—P0204. Start with a fuel pressure test under KOEO conditions to check for drops over five minutes. Look for vacuum leaks as well. Try adding SeaFoam or Techron fuel cleaner. Check spark plug condition: black, wet, or dry tan? P0204 codes often point to injector harness wiring issues—especially in 1998 Plymouth Voyagers. Verify the connector at the injector is secure and free of corrosion. Also consider performing an ohm test on injectors. Search online for known wiring harness melting problems specific to your model year.

Anonymous 2016-06-10 12:34

There are only two wires per injector: one constant 12V (same color across all injectors), and a signal/control wire that varies by injector. The signal wire should show no voltage when not firing—only open circuit, not grounded. When checking, gently shake the harness to detect loose connections. Confirm your vehicle’s model year and location for known injector harness issues. Use an OBD2 scanner to monitor other sensors during testing—such as fuel temperature (FT), ECT, MAP, and pre-cat oxygen sensor voltages. These can help identify related faults that may trigger P0204 during diagnostics.

Anonymous 2016-06-10 13:14

I tested the voltage at the three front injectors, including injector #4. All showed fluctuating readings, with each peaking at just over 9 volts—consistent across all injectors. This suggests a potential signal issue rather than a power supply problem.

Anonymous 2016-06-10 15:07

Injector #4 is located in the front center position. A reading of 9V seems low, but since all injectors show the same voltage, the issue may lie in the signal wire path to the PCM. The PCM grounds the signal wire when it commands injection and monitors voltage on that wire—P0204 indicates the expected voltage was not detected. It's essential to verify 12V at the PCM terminal for injector #4. A common cause is an open or grounded signal wire in the harness. Did you perform an ohm test on the injectors? Check front injectors and post-injector wiring. While 9V may be low, if all injectors show identical readings, it could point to a shared ground or faulty PCM signal reference—worth investigating further with known voltage thresholds for this model year.