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| Illustration 1 | g02669082 |
FNR switch connections to the FNR #2 sensor | |
A CID 2994 is associated with the Direction Selector Position #2 (FNR #2) sensor. An FMI 04 means the machine ECM has determined the sensor output signal voltage is below the expected voltage or duty cycle range.
Note: The Direction Selector Position Switch (FNR) switch is three-position rocker switch located on the Speed / Direction handle. The FNR switch contains two "Hall Effect" position sensors that provide two PWM input signals to the machine ECM. The signals are used to indicate the position of the rocker switch to the ECM. The two switch position sensors are: Direction Selector Position Sensor #1 (FNR #1) and Direction Selector Position Sensor #2 (FNR #2). When the ECM detects a problem with the FNR #1 sensor, the ECM triggers a CID 2993. When the ECM detects a problem with the FNR #2 sensor, the ECM triggers a CID 2994. The ECM will continue normal operations if only one, or the other sensor, malfunctions alone. If one sensor fails, and then the other one fails: the ECM will trigger a CID 3527 FMI 12 diagnostic code, to indicate both sensors are malfunctioning at the same time. With a CID 3527 FMI 12 diagnostic code, the ECM will force-shift the transmission to the "NEUTRAL" position, until the problem is corrected.
Possible causes for this diagnostic code are:
- FNR switch failure.
- FNR #2 sensor output grounded.
- Machine ECM failure, but is most unlikely.
Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all the machine harnesses and connectors involved in the circuit. Make sure to verify that all of the connections in the circuit are clean, secure, and in good condition. Correct any problems found with any of the connections. Verify the diagnostic code CID 2994 FMI 04 is still active, before continuing with this procedure.
Note: The following test procedure may create other diagnostic codes. Ignore all the created diagnostic codes now, but clear all those codes after the cause for the original diagnostic code has been corrected.
Test Step 1. CHECK THE FNR SWITCH.
- Turn the disconnect switch, and the key switch, to the OFF position.
- Disconnect the 12-contact harness connector from the FNR switch.
- Turn the disconnect switch, and the key switch, to the ON position.
- Observe the status of the CID 2994 FMI 04 diagnostic code.
Expected Result:
The diagnostic code remains active.
Results:
- YES - The diagnostic code remains active. The FNR switch is not the problem. Go to Test Step 2.
- NO - The diagnostic code goes inactive, and a CID 3527 FMI 12 diagnostic code becomes active.
Repair: The FNR switch sensors are not serviceable but the FNR switch is. Replace the switch. BEWARE: CID 3527 is also triggered because the FNR #1 and FNR #2 sensors are also disconnected when the FNR switch is disconnected.BEFORE REPLACING THE SWITCH: Perform Test Step #2, to verify the FNR switch failure.
Go to Test Step 3.
Test Step 2. CHECK THE FNR #2 SENSOR CIRCUITS FOR A SHORTED CONNECTION IN THE HARNESS.
The 12 contact harness connector remains disconnected from the FNR switch.
- Turn the disconnect switch, and the key start switch, to the OFF position.
- Disconnect the J1 and J2 harness connectors from the machine ECM.
- At the ECM J2 harness connector, measure the resistance between contact J2-49 (wire E947-WH) and frame ground. Measure the resistance between contact J2-49 (wire E947-WH) and all of the other contacts are used in the J1 and J2 ECM harness connectors.
- While observing the resistance measurement of the circuits, gently wiggle the machine harness near the ECM connectors and near the FNR switch connector.
Expected Result:
Each of the resistance measurements is greater than (+/-) 5000 ohms.
Results:
- YES - Each resistance measurement is greater than 5000 ohms. There are no short circuits in the harness. Go to Test Step 3.
- NO - A resistance measurement is less than 5000 ohms. There is a short circuit in the harness.
Repair: The FNR #2 sensor output signal circuit is shorted to frame ground, or to the circuit that measured the low resistance.Refer to the complete machine Electrical System Schematic. Examine all of the connectors in the circuits for points in the machine harness where a short could occur. Look for areas where the harness could be contacting the frame.Repairs or replace the harness.
Go to Test Step 3.
Test Step 3. CHECK THE DIAGNOSTIC CODE STATUS.
- Reconnect all disconnected machine harness connectors. Make sure that all the connectors are clean, and fully seated. Observe that the clips for each connector are securely fastened.
- Turn the key start switch and the disconnect switch to the ON position.
- Clear all inactive diagnostic codes.
- Operate the machine.
- Check the status of the CID 2994 FMI 04 diagnostic code.
Expected Result:
The diagnostic code is not active.
Results:
- YES - The diagnostic code is no longer active and does not exist at this time.
Repair: Return machine to normal operation.
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- NO - The diagnostic code is still active. The problem has not been corrected. The ECM may have failed.
Repair: If you have not inspected the harness connectors in a previous Test Step, do that now. Clean the contacts of the harness connectors. Check the wires for damage to the insulation caused by excessive heat, battery acid, or chafing.Perform a 45 N (10 lb.) pull test on each of the wires that are associated with the sensor circuit.Perform a "wiggle test" on the sensor circuit of the machine wiring harness, using the Caterpillar Electronic Technician service tool. The "wiggle test" can be used to detect open or shorted connections in the machine wiring harness.Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened. Perform Test Step 3 again. If the problem was again not found, and the original code is still active, the machine ECM may have failed.Prior to replacing an ECM, always contact your Dealership Technical Communicator for possible consultation with Caterpillar, or with the Dealer Solutions Network. This consultation may greatly reduce repair time. If the ECM needs to be replaced, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
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