DTC U1814
Diagnostic Instructions
DTC Descriptor
| DTC U1814 00: Powertrain Wake Up
Communication Circuit |
| DTC U1814 01: Powertrain Wake Up
Communication Circuit Short to Battery |
| DTC U1814 02: Powertrain Wake Up
Communication Circuit Short to Ground |
| DTC U1814 04: Powertrain Wake Up
Communication Circuit Open |
| DTC U1814 5A: Powertrain Wake Up
Communication Circuit Not Plausible |
Diagnostic Fault Information
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Signal Performance
|
Powertrain Serial Data Communication Enable
|
U1814, 1
|
U0100-U02FF
|
-
|
-
|
1. Vehicle will not start.
|
|
| |
Circuit/System Description
The body control module (BCM) activates the serial data
communication enable circuit when the ignition key is in ACC, ON or
START. The serial data communication enable circuit wakes up the
engine control module (ECM) for serial data bus communication.
Conditions for Running the DTC
| • |
The system voltage is between
9-16 volts. |
| • |
The vehicle power mode master
requires serial data communication to occur. |
Conditions for Setting the DTC
The BCM senses a short to ground on the serial data
communication enable 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 until the next ignition
cycle. |
| • |
The module(s) is never
signaled, therefore the specific subsystem(s) will not
function. |
| • |
The vehicle will not start
while the circuit is shorted to ground. |
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. |
| • |
Short to ground will also set
multiple history no communication codes for GMLAN high speed
modules. |
Reference Information
Schematic Reference
Data Communication Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Data Link Communications Description and Operation
Electrical Information Reference
Circuit/System Testing
Note: Use the schematic to
determine which control modules are on the BCM communications
enable circuit 22, X4.
| 1. |
Ignition OFF, disconnect the
harness connector at the most easily accessible control module on
the K9 BCM communications enable circuit. |
| 2. |
Ignition ON, retest for
current DTCs. DTC U1814 should remain current. |
| ⇒ |
If the DTC becomes history, replace the control
module that was just disconnected. |
| 3. |
With the prior control modules
disconnected, repeat steps 1 and 2 for each control module on the
circuit except the K9 BCM. |
| 4. |
Ignition OFF, disconnect the
X4 harness connector at the K9 BCM. |
| 5. |
Test for infinite resistance
between the serial data communication enable circuit terminal 22 X4
and ground. |
| ⇒ |
If less than infinite resistance, repair the
communications enable circuit for a short to ground. |
| 6. |
If all circuits tests normal,
replace the K9 BCM. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
Control Module References for module replacement, setup, and
programming
|
