Table 1. 291 Demand Fan Solenoid Diagnostic Codes.
CID FMI CODE
TEST OR INSPECTION
291-3 Demand Fan Solenoid
Voltage Is Above Normal
· Always inspect wiring 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 wiring harness connection to
identify the correct wiring harness to replace.
· Tag all wiring harnesses to aid in installation.
· Perform this test only if condition is active.
DIAGNOSTIC CODE SET CONDITION
Transmission ECM detects voltage of the demand fan solenoid is above normal.
· Lower cab wiring harness is shorted to another power source.
· Rear frame wiring harness is shorted to another power source.
· Transmission ECM.
Test Step 1. Check for Active
Connect MSD. Select Transmission
Diagnostic Code 291-3 Active -
924H and check for active diagnostic
Proceed to Test Step 2.
Diagnostic Code 291-3 Not Active -
Troubleshooting is complete.
Test Step 2. Test for Shorted Rear
Frame Wiring Harness.
1. Turn ignition switch and battery
disconnect switch to OFF position
2. Remove fan (WP 0234).
3. Disconnect connector M-C16
demand fan solenoid.
4. Remove right lower cab access
panels (WP 0347).