The P1389 code on Jeep vehicles (Stellantis group) is related to the ASD (Auto Shutdown Relay) relay circuit, a key component that supplies electricity to essential engine elements such as the injectors, ignition coil, or crankshaft sensor. Here is a complete guide to diagnose and resolve this issue.
Meaning of the P1389 Code
The ASD relay acts as a safety switch controlled by the Powertrain Control Module (PCM). It cuts off electrical power in case of a critical anomaly (e.g., absence of signal from the crankshaft sensor). The P1389 code is stored when the PCM detects a malfunction in the ASD relay circuit, such as irregular voltage or a missing signal.
Possible Causes
- Faulty ASD Relay:
- Oxidized, stuck, or worn internal contacts.
- Electrical Issues:
- Blown fuse (often in the under-hood fuse box).
- Cut wires, short circuit to ground, or corroded connectors.
- Crankshaft Sensor Failure:
- An erroneous signal disrupts the ASD relay operation.
- PCM Failure (rare).
Common Symptoms
- 🚨 Engine light on (Check Engine).
- 🔌 Engine stalling abruptly or not starting.
- ⚡ No spark or fuel injection (diagnosed via OBD2 scanner).
Diagnosis and Repairs
Verification Steps
- Check the ASD Fuse:
- Locate the fuse associated with the ASD relay (refer to the Jeep manual). Replace it if blown.
- Test the ASD Relay:
- Swap it with an identical relay (e.g., headlight relay) to check its operation.
- Test continuity and resistance with a multimeter (expected: ~50-120 ohms).
- Inspect the Crankshaft Sensor:
- Check its connector and wiring. Test its resistance (generally 200-1000 ohms depending on the model).
- Check the Electrical Circuit:
- Look for exposed wires, melted insulation, or oxidized connectors between the PCM, ASD relay, and battery.
Common Solutions
- Replace the ASD Relay:
- Cost: €15 to €50. Opt for a compatible part (e.g., Mopar for Jeep).
- Repair the Wiring:
- Insulate damaged wires with heat shrink tubing.
- Replace the Crankshaft Sensor (if necessary).
Affected Jeep Models
This code is common on Jeeps equipped with 3.7L, 4.0L, or 4.7L engines, including:
- Jeep Grand Cherokee (WJ/WK)
- Jeep Wrangler (TJ/JK)
- Jeep Liberty (KJ/KK).
Safety Tips
- 🔋 Disconnect the battery before any electrical work.
- 🔧 Consult a repair manual specific to your Jeep model to locate the ASD relay (often in the PDC box under the hood).
Resetting the Code
- Use an OBD2 scanner to clear the P1389 code after repair. Perform a test drive to confirm resolution.
When to Consult a Professional?
If the code persists after replacing the ASD relay and checking the circuit, a garage can:
- Diagnose a possible PCM failure.
- Analyze the crankshaft sensor signal with an oscilloscope.
In summary: The P1389 code on Jeep indicates a problem with the ASD relay circuit. Prompt action prevents unpredictable engine failures and ensures vehicle reliability.