How to Fix the Service 4WD Light on a Jeep Patriot

Hello guys, today we’re going to diagnose and fix the Service 4WD Light in my Jeep Patriot. This step-by-step guide will help you understand the problem, find the root cause, and fix it effectively.

Diagnosing the Service 4WD Light

Step 1: Initial Diagnosis

1. Turn on the Ignition: Start by turning on the ignition. You will see that there is no problem putting the vehicle into four-wheel drive mode while it is parked. However, as soon as the car moves, the 4WD light comes on.
2. Scan for Trouble Codes: Using a scan tool, check for any trouble codes. In this case, I received a trouble code that indicated an issue with the 4WD system.

Step 2: Check the Fuse Box

Since the 4WD system is electronically controlled, the next step is to check the fuse box.

1. Locate the Fuse Box: The fuse box in the Jeep Patriot is located under the hood. Refer to the user manual to identify the fuse for the four-wheel drive system, which is fuse number two.
2. Test the Fuse: Using a test light, check for power on both sides of the fuse. If the fuse is good, proceed to check the power supply to the four-wheel drive module.

Step 3: Check the Four-Wheel Drive Module

The four-wheel drive module is located behind the left corner panel on the driver’s side.

1. Remove the Corner Panel: Start by removing the clip and then the trim by pulling it up. Pull back the corner panel to access the module.
2. Disconnect the Connector: Use a screwdriver to push and hold the clip inward, then gently pull the wire harness to disconnect it.
3. Check for Battery Power: Ensure there is battery power to the red and white wire.
4. Check for Switched Power: With the ignition off, there should be no power to the pink and gray wire. Turn the ignition on, and there should be power.

Step 4: Check the Ground Connection

1. Test for Continuity: Ensure there is continuity between a good ground point and the black wire. If the ground is good, there are no power issues.

Step 5: Check the Control Wires

1. Solenoid Control Wire: Check the yellow and violet wire to ensure it is not grounded. There should be no short to ground.
2. Voltage Supply Wire: Check the yellow and black wire for continuity. There should be no short to ground.

Diagnosing Further

Step 6: Check Continuity to the ECC Connector

The ECC connector is located in front of the transfer case.

1. Disconnect the ECC Connector: Get under the car and peel back the shield a little bit. Use a screwdriver to push the tab upward and wiggle the connector until it comes off.
2. Test Continuity: Check the continuity of the yellow and violet wire between the two connectors. Repeat the test for the yellow and black wire. If there is resistance, there may be an open circuit somewhere.

Step 7: Locate the Open Circuit

To determine if the open circuit is inside or outside the car:

1. Remove Plastic Panels: Gain access to another connector by removing some plastic panels in the back. Remove the screws and pull back the panels.
2. Test Continuity: Back probe the yellow and black wire and check for continuity to the ECC connector. If there is no continuity, the open circuit is in the ECC wire harness outside the car.

Fixing the Problem

Step 8: Repair the Damaged Wire

1. Locate the Damage: After pulling out the wire from the loom, look for any damage. In this case, the damage was just above the drive shaft.
2. Repair the Wire: Repair the wire using a heat shrink butt connector. Ensure a solid connection and protect it with a heat shrink tube and heat-resistant electrical tape.
3. Reconnect the Connectors: Reconnect the ECC connector and the four-wheel drive connector.

Testing the Fix

Step 9: Test the 4WD System

1. Start the Car: Start the car and engage the four-wheel drive mode. Begin moving the car to check if the 4WD light comes on.
2. Check the Light: If the light does not come on, the problem is fixed. You should be able to switch between four-wheel drive mode and front-wheel drive without any issues.

Conclusion

We have successfully diagnosed and fixed the Service 4WD Light on the Jeep Patriot with minimal cost. This DIY fix can save you money and time. Always ensure you have the right tools or can borrow them if needed.