Owner's Problem Description
The owner's 1995 Chrysler Sebring is turning over but not cranking. Recent actions include replacing the distributor, checking the timing, and installing new spark plugs and wires. Despite these efforts, the vehicle fails to crank, leaving the owner in need of further assistance. The owner has attempted using starter fluid, which resulted in a momentary start before the engine cut off and has since not worked again.
Professional Technical Analysis
The 1995 Chrysler Sebring is equipped with a 2.5L V6 engine, and based on the owner's description, the vehicle's symptoms include the engine turning over without starting. The vehicle has been subjected to a series of component replacements, including a new distributor and spark plugs, indicating an active troubleshooting process. The owner reports that the engine briefly cranked after the use of starter fluid, suggesting intermittent fuel or spark issues. Given that the vehicle is not generating a crank signal at the Powertrain Control Module (PCM), it is imperative to investigate the ignition system thoroughly, focusing on potential causes such as the Ignition Control Module (ICM), the crankshaft position sensor, or issues within the PCM itself. The absence of a crank signal may stem from faulty wiring, poor connections, or an internal PCM malfunction. Considering the system interconnections, the ignition system's performance is directly tied to the PCM's ability to receive and process input signals from the crankshaft and camshaft position sensors. The vehicle's previous repair history, particularly the replacement of the water pump, could suggest a connection to the timing belt system, which may impact sensor alignment if improperly installed. In this context, it is essential to evaluate the crankshaft position sensor's signal, ensuring proper voltage and resistance values, typically around 0.5-2.0V with an expected frequency of 2-3V during cranking. Additionally, verifying that power is reaching the ignition coil and distributor is crucial for diagnosing the no-start condition. A comprehensive assessment of the vehicle's current condition indicates the need for immediate diagnostic testing to rule out critical failure points.
Possible Causes
Most common causes (ordered by frequency):
- Ignition Control Module (ICM) Failure: The ICM may be malfunctioning, preventing spark generation. This module typically fails under heat stress and can lead to intermittent starting issues. Confirm ICM operation by checking for proper voltage (12V) and signal output when cranking. Replacement may be necessary if the unit shows signs of overheating or internal failure. - No spark detected at the spark plugs during cranking, intermittent operation when the ICM is hot, potential stored codes related to ignition system failure.
- Crankshaft Position Sensor (CKP) Malfunction: A faulty CKP sensor can prevent the PCM from receiving the necessary crank signal. When testing, ensure the sensor output voltage is between 0.5V and 2.0V during cranking, with a frequency of 2-3V. If readings are outside this range, replacement may be required. - No crank signal detected at the PCM, intermittent signal during testing, possible stored codes related to CKP failure.
- PCM Failure: If the PCM itself is malfunctioning, it may fail to provide the necessary signals for the ignition system to operate. Testing should include checking for power and ground at the PCM connectors. If the PCM shows no response or communication during diagnostics, replacement may be required. - No communication with the scanner, power and ground tests at PCM connectors fail.
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 Scan: Begin by performing a comprehensive scan using a professional OBD-II scanner or the GeekOBD APP. Retrieve any stored fault codes and examine freeze frame data for relevant information regarding the engine's operating conditions prior to the no-start issue. This will help identify potential faults in the ignition system or sensor failures.
- STEP 2 - Verify Power at Ignition Components: Check the voltage supply to the ignition coil and ICM. Ensure that there is a stable 12V supply when the ignition is turned on. If not, trace back through the wiring to find any shorts or open circuits that may be affecting the ignition system's operation.
- STEP 3 - Test Crankshaft Position Sensor: Using a multimeter, check the output from the CKP sensor while cranking the engine. The voltage should be within the specified range (0.5-2.0V). If the output is outside this range, replace the CKP sensor and retest.
- STEP 4 - PCM Testing: If previous steps do not reveal the issue, check for power and ground at the PCM connectors. If power is present and the PCM is still unresponsive, further diagnostics or replacement may be needed. This may require specialized tools for in-depth testing.
