420D, 428D, 430D, 432D, 438D, 442D and 446B Backhoe Loaders Power Train Electronic Control System Caterpillar

MID 081 - CID 0368 - FMI 06

Usage:

446B 5BL

Conditions Which Generate This Code:

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Illustration 1	g00753129
Schematic for the Autoshift Switch Circuit

This diagnostic code is recorded when the status of both the normally open inputs and the normally closed inputs are grounded. Both inputs will have the same grounded condition. The switch has two inputs to the ECM. The inputs are normally open and normally closed. During proper operation, one input is open and the other input is grounded.

The possible causes of this diagnostic code are listed:

The machine harness has failed.
The ground circuit to the switch is shorted.
The Auto/Manual switch has failed.
The ECM has failed. This is unlikely.

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Table 1
Auto/Manual Switch Status ⁽¹⁾
Switch Position	973-BR Circuit Contact 1 (N/O)	977-YL Circuit Contact 3 (N/C)
Auto	Open ⁽²⁾	Grounded ⁽³⁾
Manual	Grounded ⁽³⁾	Open ⁽²⁾

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^( 1 )	B Series machines
^( 2 )	A typical resistance measurement for an open is greater than 5000 ohms.
^( 3 )	A typical resistance value for a circuit that is grounded is less than 5 ohms.

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Table 2
Auto/Manual Switch Status ⁽¹⁾
Switch Position	973-BR Circuit Contact 4 (N/C)	977-YL Circuit Contact 6 (N/O)
Auto	Open ⁽²⁾	Grounded ⁽³⁾
Manual	Grounded ⁽³⁾	Open ⁽²⁾

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^( 1 )	D Series machines
^( 2 )	A typical resistance measurement for an open is greater than 5000 ohms.
^( 3 )	A typical resistance value for a circuit that is grounded is less than 5 ohms.

System Response:

If an active diagnostic code is present, the system will default to the manual mode after 5 seconds. The operator will be unable to toggle the system to the Auto function.

Test Step 1. CHECK THE GROUND CIRCUIT OF THE HARNESS .

Turn the key start switch to the OFF position.

For 446B and 446D: At the terminals for the switch, measure the resistance between contact 2 (wire 202-BK) and frame ground. For all other machines, measure the resistance between contact 5 (wire 202-BK) and frame ground.

Expected Result:

The resistance is 5.0 ohms or less.

Results:

YES - The resistance is 5.0 ohms or less. The ground circuit for the harness is correct. Proceed to test step 2.
NO - The resistance is greater than 5.0 ohms. The ground for the harness has failed.
Repair: Wire 202-BK is open in the harness between the switch and frame ground. Repair the harness or replace the harness.
Stop.

Test Step 2. CHECK THE SWITCH

Turn the key start switch to the OFF position.

Disconnect the auto/manual switch.

Measure the resistance between each contact terminal of the switch to ground.

Observe the measurement while you activate the auto/manual switch and you deactivate the auto/manual switch.

Expected Result:

When the switch is ACTIVATED, the resistance should measure less than 5 ohms. When the switch is NOT ACTIVATED, the resistance should measure more than 5000 ohms.

Results:

YES - The resistance is within an acceptable range. The auto/manual switch is functioning correctly. Proceed to test step 3.
NO - The resistance is not within an acceptable range. The switch has failed.
Repair: Repair the switch or replace the switch.
Stop.

Test Step 3. CHECK THE SWITCH INPUTS

The key start switch remains in the OFF position.

Disconnect the auto/manual switch.

Measure the resistance between the two contact terminals of the switch.

Observe the measurement while you activate the auto/manual switch and you deactivate the auto/manual switch.

Expected Result:

The resistance should measure more than 5000 ohms as the switch is toggled.

Results:

YES - The resistance that is measured is greater than 5000 ohms as the switch is toggled. Proceed to test step 4.
NO - The resistance is less than 5000 ohms. There is a short between the contact terminals for the switch.
Repair: Repair the switch or replace the switch.
Stop.

Test Step 4. CHECK THE HARNESS CIRCUIT.

Turn the key start switch to the OFF position.

Replace the wire that was removed in the previous test step.

Disconnect the harness from the ECM.

At the harness connector for the ECM, check the resistance to ground of the normally closed contact and the normally open contact. Activate the switch when this check is being performed. See Table 1 or 2 for the proper contacts.

Expected Result:

The resistance does not agree with the value in Table 1 or 2.

Results:

YES - The resistance does not agree with the value in the preceding table.
Repair: The harness circuit has failed. There is an open in the harness between the ECM and the switch. Repair the harness or replace the harness.
Stop.
NO - The resistance agrees with the value in the preceding table. The harness circuit is correct.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this troubleshooting procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
Stop.