U1814

DTC U1814

DTC DESCRIPTOR

DTC U1814 00
Powertrain High Speed Communication Enable Circuit

DIAGNOSTIC FAULT INFORMATION




Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

Powertrain HS Comm. Cmd.:

TYPICAL SCAN TOOL DATA

CIRCUIT/SYSTEM DESCRIPTION
The accessory voltage signal circuit is a positive voltage signal to wake up the engine control module (ECM) and the transmission control module (TCM). The signal is activated in 2 ways. Any time the ignition switch is in the ACC or RUN position, or anytime the body control module (BCM) determines that communication is needed from the powertrain. When the ignition switch is in the ACC or RUN position, the input to the BCM is internally connected to the accessory voltage signal circuit, and voltage is supplied. The BCM supplies voltage to the accessory voltage signal when it determines that communication is necessary with the powertrain and the ignition is not in the ACC or RUN position such as during remote start.

CONDITIONS FOR RUNNING THE DTC
The system voltage is between 9-16 volts.

CONDITIONS FOR SETTING THE DTC
The BCM senses a short to ground on the accessory voltage signal circuit.

ACTION TAKEN WHEN THE DTC SETS
The output command is turned off while the malfunction is present.

The modules use a default value for the missing parameters.

The vehicle may not start.

CONDITIONS FOR CLEARING THE DTC
- A current DTC clears when the malfunction is no longer present.
- A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

DIAGNOSTIC AIDS
Use the DMM MIN/MAX function to capture/locate intermittent conditions.

CIRCUIT/SYSTEM VERIFICATION
Use the scan tool to observe the Powertrain HS Comm. Cmd. parameter in the BCM data list, while turning the ignition switch. The reading should match the normal range of the typical scan tool data above.

If all parameters are all correct and the DTC is current, replace the BCM.

CIRCUIT/SYSTEM TESTING
1. With the ignition OFF, disconnect the harness connector at the ECM and TCM one at a time. After each disconnect, retest for current DTCs. DTC U1814 should remain current.
- If the DTC becomes history, replace the module disconnected before the DTC became history.
2. Ignition OFF, disconnect the harness connector at the BCM.
3. Test for infinite resistance between the accessory voltage signal circuit and ground.
- If less than infinite resistance, repair the signal circuit for a short to ground.
4. If all tests normal, replace the BCM.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Refer to Control Module References for module replacement, setup, and programming. Programming and Relearning