Owner's Problem Description
The owner reports that the oil light comes on suddenly while driving, and shortly after, there is a loss of pressure on the gas pedal, resulting in no fuel delivery. The engine does not die but requires pulling over and shutting off the car. After replacing the oil pressure sensor, the issue reoccurred after driving about 15 miles, resting for 30 minutes, and then driving another 12-13 miles. The owner is frustrated and seeking help, suspecting a connection to the PCM or PCM relay.
Professional Technical Analysis
This 2004 Chrysler Sebring, equipped with a 2.4L inline-4 engine, has displayed a concerning symptom where the oil light illuminates suddenly, leading to a loss of gas pedal pressure and fuel delivery. The vehicle has approximately 120,000 miles on it. Upon initial analysis, the oil pressure sensor was recently replaced, indicating a potential oversight in diagnosing the root cause of the oil pressure warning. This symptom often suggests either a genuine oil pressure issue or an electrical fault impacting the PCM's ability to manage fuel delivery. The oil light's illumination can trigger a safety protocol in the PCM that cuts fuel delivery to prevent engine damage, which may explain the loss of gas pedal response. Furthermore, given the intermittent nature of the AC performance prior to these issues, it raises concerns about potential electrical system instability, possibly affecting both the fuel and HVAC systems. It is crucial to perform a diagnostic scan to check for any stored fault codes related to the PCM, oil pressure sensor, and fuel delivery system, as well as to analyze live data to monitor oil pressure readings and PCM responses during operation. Current vehicle conditions show that the engine doesn't stall but loses fuel pressure, indicating possible PCM or relay failure. Continuous monitoring and a systematic approach to diagnosis are necessary to prevent further issues.
Possible Causes
Most common causes (ordered by frequency):
- Oil Pressure Sensor Failure: If the oil pressure sensor is malfunctioning, it can incorrectly signal the PCM to cut fuel delivery, leading to sudden loss of throttle response. This can be confirmed by observing the oil pressure readings on a live data scan, which should typically be between 10-70 PSI at idle. A faulty sensor may show erratic readings or drop to zero pressure despite the engine running. Replacement part: OEM P/N 04891781AA. - Observed sudden oil light illumination, loss of throttle response, erratic oil pressure readings post-replacement.
- PCM Malfunction: A failure within the PCM could lead to improper control of fuel delivery systems, especially if there are internal faults or software glitches. This can manifest as fuel delivery cut-off under certain conditions, particularly when the oil pressure sensor signals a fault. Diagnostic trouble codes (DTCs) should be retrieved to confirm any PCM-related issues. Typical conditions for PCM failure include water damage or electrical surges. - Check engine light activation, issues with fuel delivery, potential DTCs related to PCM functionality.
- Fuel Pump Relay Failure: The fuel pump relay may be intermittently failing, causing the fuel pump to stop delivering fuel when the oil light comes on. This could be due to aging components or poor electrical connections. A relay typically should have continuity when energized and a functioning pump should deliver at least 35-45 PSI. Testing the relay and pump under load is essential to confirm this. - Loss of fuel delivery coinciding with oil light illumination, potential issues with relay operation.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Initial Diagnostic Scan: Begin with a thorough OBD-II scan using a professional scanner or GeekOBD APP. Retrieve any stored fault codes related to the PCM, oil pressure sensor, and fuel system. Pay special attention to any DTCs indicating a malfunctioning PCM or communication errors. Document any freeze frame data available for context during the issue's occurrence.
- STEP 2 - Check Oil Pressure: Using a mechanical oil pressure gauge, check the actual oil pressure while the engine is running. The pressure should typically be between 10-70 PSI at idle; any readings below this range may indicate genuine oil pressure issues or a faulty sensor. This helps rule out mechanical failures within the engine that could cause low oil pressure.
- STEP 3 - Relay and Fuel Pump Test: Inspect the fuel pump relay and perform a continuity test to ensure it activates properly. If the relay is faulty, replace it with an OEM part (OEM P/N 04891781AA). Additionally, check the fuel pump output pressure to confirm it meets the specification of 35-45 PSI under load conditions.
- STEP 4 - Live Data Monitoring: Utilize the GeekOBD APP to monitor live data during a test drive. Focus on oil pressure readings, PCM response times, and fuel trim adjustments. Document any discrepancies in expected values, as these can indicate the underlying issues affecting fuel delivery and engine performance.
