ROD AS. 1551683 - Caterpillar

Illustration 1 g01305868
Connections of "Secondary Steer Request" signal circuit
This diagnostic code is associated with the "secondary steer request" signal circuit. This circuit enables the Implement ECM to request that the Transmission/Chassis ECM activate the secondary steering system when certain machine conditions require it. The FMI 04 means that the Transmission/Chassis ECM has detected that a lower than normal voltage is present in the circuit.When a CID 2199 diagnostic code is activated by the Transmission/Chassis ECM, the ECM will activate the secondary steering system without input from the Implement ECM. This is the only condition that will cause the Transmission/Chassis ECM to activate the secondary steering system without input from the Implement ECM.During normal operation, when the Implement ECM detects a problem in the primary steering system, the Implement ECM will send a pulse width modulated (PWM) signal to the Transmission/Chassis ECM on the circuit for the secondary steering request that is connected between the two controls.When the Implement ECM sends a PWM secondary steering request signal to the Transmission/Chassis ECM, the duty cycle of the PWM signal will determine the specific secondary steering system components that will be activated. During normal operation, the Implement ECM maintains a 20 percent duty cycle on the request circuit. When a secondary steer test is requested or when the Implement ECM has detected a problem in the primary steering system, the secondary steering request signal will be one of the following duty cycle signals:20 percent PWM duty cycle - Normal operation, no request to activate.40 percent PWM duty cycle - Request to activate the secondary steer pump motor only.60 percent PWM duty cycle - Request to activate the secondary steer pilot solenoid valves only.80 percent PWM duty cycle - Request to activate the secondary steer pump and the secondary steer pilot solenoid valves.Conditions that can cause this diagnostic code to be activated are listed below:
The circuit is shorted to a ground source.
The ECM has failed. This is unlikely. Note: Before performing this procedure, inspect the 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, that all connections are secure and that all connections are in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure. Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the problem has been corrected.Test Step 1. CHECK THE CIRCUIT FOR A SHORT TO GROUND
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connectors J1 and J2 from the Implement ECM and from the Transmission/Chassis ECM.
At the J2 machine harness connector for the Transmission/Chassis ECM, measure the resistance from contact J2-25 (wire U753-BR(Brown)) to frame ground. Measure the resistance from contact J2-25 (wire U753-BR(Brown)) to all of the other J1 and J2 contacts