Owner's Problem Description
The owner of a 1998 Dodge Intrepid reports issues while driving, including stalling, lurching, and hard starting. The check engine light has illuminated, and upon scanning, two trouble codes were retrieved: P0355 and P1391. The owner suspects ignition system problems but is unsure if the issue lies with the cam or crank sensors, PCM, or coil packs. They seek guidance on further diagnostic steps to isolate the issue.
Professional Technical Analysis
This 1998 Dodge Intrepid is equipped with a 3.5L V6 engine, automatic transmission, and has approximately 150,000 miles on the odometer. The owner reports intermittent stalling and lurching during acceleration, alongside difficulty starting the engine. The diagnostic codes P0355 (Ignition Coil 5 Primary Circuit) and P1391 (Intermittent Loss of Cam or Crank Sensor) indicate potential issues within the ignition and sensor systems. The P0355 code suggests a possible fault with ignition coil number 5, which could lead to excessive current draw, while P1391 hints at an intermittent failure of the cam or crankshaft position sensors. Given the interconnectivity of the ignition system, a failure in one component can affect others. For instance, a faulty crank sensor may mislead the PCM, causing erratic ignition timing and fuel delivery, resulting in stalling. Furthermore, the vehicle's history of maintenance and environmental factors, such as humidity or heat, could exacerbate these issues. A thorough inspection of the wiring harness, sensor connectors, and coil pack integrity is essential, as well as checking for any signs of wear or damage. Safety concerns regarding stalling while driving necessitate prompt attention to this diagnosis and repair process.
Possible Causes
Most common causes (ordered by frequency):
- Ignition Coil 5 Failure: The P0355 code indicates that the ignition coil number 5 has an excessive primary circuit current draw, likely due to internal shorting or insulation breakdown within the coil. This can lead to misfiring, backfiring, and stalling, particularly when the engine is under load. The ignition coil should be tested for resistance (expected value 0.4-2.0 ohms) and inspected for physical damage. Replacement should be with OEM part 56027931AA, costing approximately $50-100. - Check engine light illuminated, misfiring at higher RPMs, excessive current draw readings during coil testing.
- Camshaft or Crankshaft Sensor Intermittent Failure: The P1391 code indicates a potential intermittent failure of the camshaft or crankshaft position sensors. These sensors provide critical information to the PCM for timing adjustments. If either sensor fails or has a bad connection, it can lead to stalling and difficulty starting. Testing should include verifying sensor voltages (typically 0.5V-4.5V), checking for continuity in the wiring harness, and inspecting connectors for corrosion. Replacement sensors should meet OEM specifications, costing around $40-80 each. - Intermittent stalling, difficulty starting, and stored P1391 code indicating possible sensor failure.
- Wiring Harness Issues: Although the chance of a wiring harness failure is low, damaged or corroded connections between the ignition coil and the PCM could create intermittent faults. Visual inspection of the wiring harness for fraying, corrosion, or loose connections is essential. Any damaged sections should be repaired or replaced. This may involve costs around $100-200 for labor if extensive repairs are needed. - Visual inspection shows signs of wear or corrosion on connectors, intermittent connectivity issues during testing.
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 OBD-II Diagnosis: Utilize a professional OBD-II scanner or the GeekOBD APP to retrieve stored trouble codes, including freeze frame data to assess conditions when the codes were triggered. Take note of any additional codes that may provide context to the primary issues at hand. This step ensures a comprehensive understanding of the vehicle's diagnostic state before proceeding.
- STEP 2 - Live Data Analysis: Use the GeekOBD APP’s live data monitoring feature to track real-time parameters such as ignition timing, fuel trim, and sensor voltages. Pay attention to the readings from the crank and cam sensors, which should show stable output voltages under normal operating conditions. Document any inconsistencies or fluctuations that occur during symptom manifestation.
- STEP 3 - Component Testing: Test the ignition coil by measuring resistance and checking for proper voltage at the connector. Coil number 5 should show resistance values between 0.4-2.0 ohms. Check the cam and crank sensors for proper voltage outputs (0.5V-4.5V) and continuity in the harness. Utilize the GeekOBD APP for advanced diagnostics to verify sensor operation and integrity.
- STEP 4 - Road Test with Data Logging: Conduct a controlled road test while monitoring live data using the GeekOBD APP. Observe how the vehicle behaves under different load conditions, noting any failure patterns or anomalies in engine performance. This can help isolate whether the issue is more related to the ignition system or the sensors.
