Owner's Problem Description
The owner reports that their 1993 Dodge Grand Caravan with a 3.3L V6 engine won't start. The vehicle cranks but does not fire. Previous attempts include checking for diagnostic codes by cycling the ignition but found no engine light or codes. The fuel pump activates, but there is no spark to the ignition coil or injectors. The owner is concerned about possible issues with the camshaft sensor, ignition module, or the ASD relay. The current condition is frustrating as the vehicle is inoperable.
Professional Technical Analysis
This 1993 Dodge Grand Caravan is equipped with a 3.3L V6 engine and an automatic transmission. The owner reports that the vehicle cranks but does not start, indicating a potential issue in the ignition or fuel delivery systems. With approximately 150,000 miles on the odometer, the vehicle's age and mileage suggest that components such as the ignition control module (ICM) or the camshaft position sensor (CMP) could likely be failing. The absence of check engine light during diagnostic code retrieval suggests a malfunction in the ASD relay or failure to receive proper signals from the crankshaft and camshaft sensors. The ASD relay powers the ignition coil and injectors, and if these circuits are not receiving voltage, the vehicle will not start. Normal operation of the ignition system requires a stable voltage supply, typically around 12V during cranking. If the voltage at the ignition coil's dark green wire with orange tracer is not present while cranking, further investigation into the ASD relay and associated wiring is necessary. Additionally, checking for proper ground signals from the PCM is crucial, as a failure in these circuits can prevent the relay from engaging. Given the vehicle's condition, safety concerns arise if the issue is not resolved, especially if the vehicle fails unexpectedly while driving.
Possible Causes
Most common causes (ordered by frequency):
- ASD Relay Failure: The ASD relay is responsible for supplying power to the ignition coil and fuel injectors. If the relay fails, it can prevent voltage from reaching these components, causing a no-start condition. Check the relay for continuity and proper operation; it should click when activated. If not, replace with OEM part number 56028171AA, which costs approximately $30. - No voltage present at the ignition coil or fuel injectors, relay not clicking during activation.
- Camshaft Position Sensor Failure: A faulty CMP can prevent the PCM from receiving the necessary signals to activate the ASD relay. This model is known to have issues with the CMP sensor, particularly after 100,000 miles. Testing should reveal a resistance of 500-1500 ohms; if outside this range, replacement is needed with part number 56027831AA, costing around $50. - No signal detected during testing, possible stored fault codes related to CMP.
- Ignition Control Module (ICM) Malfunction: The ICM controls the ignition timing and can fail, especially under high temperatures. If the ICM fails to ground the ASD relay, no spark will be generated. Testing should include checking resistance values between 1-3 ohms; if faulty, replace with part number 56028177AA, costing approximately $120. - Check engine light may illuminate intermittently, no spark detected at the ignition coil.
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 Code Retrieval: Begin with a complete scan using a professional OBD-II scanner or the GeekOBD APP to check for stored or pending codes. Given the vehicle's symptoms, it is critical to check for crankshaft and camshaft sensor signals. If no codes are retrieved, proceed to check the ASD relay and power supply to the ignition components.
- STEP 2 - Voltage Testing at Coil and Injectors: Use a multimeter to measure voltage at the dark green wire with orange tracer at the ignition coil and fuel injectors while cranking the engine. The voltage should be approximately 12V if the ASD relay is functioning properly. If not, check the relay and associated wiring for faults.
- STEP 3 - Sensor Signal Testing: Check the crankshaft and camshaft position sensors for proper operation. Use an oscilloscope to verify signal waveform integrity. Resistance testing should reveal values within specified ranges. If any sensor is faulty, replace it with the appropriate OEM part.
- STEP 4 - Relay Functionality Check: Test the ASD relay by applying direct power to the relay terminals to confirm if it clicks and activates. If the relay does not engage, it should be replaced. Use the GeekOBD APP to monitor voltage changes when the relay is activated.
