Troubleshooting 0.9 Error Code from Tekonsha Prodigy P2 Brake Controller 90885  

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When the Tekonsha Prodigy P2 # 90885 brake controller displays the error message 0.9 this indicates that the controller senses a connected trailer but is losing its ground connection to the vehicle battery ground. The white wire on the brake controller harness is ground so you can check the condition of the electrical contacts for this wire on both the vehicle and controller ends of the wiring adapter. Look for a bent or damaged metal contact. Also, even slight greenish or whitish discoloration can indicate corrosion that could be causing the ground interruption. Repair or replace the harness as needed.

Since you are seeing this error message even without a trailer connected this suggests that there could be a problem in the truck's 7-way socket or wiring. Corrosion in the socket or its connector could cause two circuits to become bridged together; this could create a signal that can fool the controller into thinking it senses the trailer's brake circuit.

If you have a circuit tester like # PTW2993 and can detect a brake signal on the 5-o-clock pin on the 7-way when a helper applies the controller's manual override, then you know the controller still operates. If you get no brake signal at the 7-way, then you'll want to test the blue wire exiting the controller; this carries the output signal for the trailer brakes. If there is no signal on the blue wire at the back of the controller when the override is pressed, then the unit is damaged internally and should be replaced.

expert reply by: Adam R

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