Table 1. 1273 Module Communication Diagnostic Code.
TEST OR INSPECTION
1273-09 Chassis Control
Module Abnormal Update
· Always inspect harness connectors that are involved in the circuit. Poor
connections can often be the cause of a problem in an electrical circuit.
Verify that all connections in the circuit are clean and secure and that all
connections are in good condition. If a problem with the connection is
found, correct the problem and verify that this malfunction or diagnostic
code is active before performing this procedure.
· Perform open or short-circuit test at each harness connection to identify
the correct harness to replace.
· Tag all wiring harnesses to aid in installation.
· Perform this test only if condition is active.
DIAGNOSTIC CODE SET CONDITION
Transmission/Chassis Electronic Control Module (ECM) Fails to Communicate
with Engine ECM.
· Fuse F20 Open.
· Main Cab Wiring Harness High Resistance, Open, or Shorted.
· Fuse Panel Wiring Harness High Resistance, Open, or Shorted.
· Circuit Breaker Panel.
· Transmission/Chassis ECM.
Test Step 1. Test for Open Fuse F20.
1. Turn ignition switch and battery
disconnect switch to OFF position
2. Remove fuse F20 from circuit
Continuity Proceed to Test Step 2.
No Continuity Discard fuse F20.
between terminals of fuse F20.
Proceed to Test Step 6.
Test Step 2. Test Main Relay Supply
Voltage at Circuit Breaker Panel.
1. Turn battery disconnect switch and
ignition switch to ON position