899912007 Mercury TAPPET, (3.138)

Table 1
Diagnostic Trouble Codes
CDL Code Description
(code descriptions may vary) Comments
1720–5 Turbocharger Compressor Bypass Valve Actuator : Current Below Normal There is low current flow in the wiring between the turbocharger compressor bypass valve and the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
1720–6 Turbocharger Compressor Bypass Valve Actuator : Current Above Normal There is excessive current flow in the wiring between the turbocharger compressor bypass valve and the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
1720–7 Turbocharger Compressor Bypass Valve Actuator : Not Responding Properly The turbocharger compressor bypass valve is not responding properly to commands from the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
1720–8 Turbocharger Compressor Bypass Valve Actuator : Abnormal Frequency, Pulse Width, or Period The turbocharger compressor bypass valve is not responding properly to commands from the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
3482–3 Sensor Supply #3 : Voltage Above Normal There is excessive voltage on the 5 VDC wire between the turbocharger compressor bypass valve and the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
3482-4 Sensor Supply #3 : Voltage Below Normal There is low voltage on the 5 VDC wire between the turbocharger compressor bypass valve and the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
4781–3 Engine Turbocharger Compressor Bypass Valve Control Module : Voltage Above Normal There is excessive voltage on the voltage supply wire to the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
4781–4 Engine Turbocharger Compressor Bypass Valve Control Module : Voltage Below Normal There is low voltage on the voltage supply wire to the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
4781–5 Engine Turbocharger Compressor Bypass Valve Control Module : Current Below Normal There is low current flow in the wiring between the engine ECM and the turbocharger compressor bypass valve controller. The code is logged.
4781–6 Engine Turbocharger Compressor Bypass Valve Control Module : Current Above Normal There is excessive current flow in the wiring between the engine ECM and the turbocharger compressor bypass valve controller. The code is logged.
5005–3 Turbocharger Compressor Bypass Valve Position Sensor : Voltage Above Normal There is excessive voltage on the signal wire between the turbocharger compressor bypass valve and the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
5005–4 Turbocharger Compressor Bypass Valve Position Sensor : Voltage Below Normal There is low voltage on the signal wire between the turbocharger compressor bypass valve and the turbocharger compressor bypass valve controller. The code is logged. Engine power is derated.
Follow the troubleshooting procedure in order to identify the root cause of the problem. System OperationThe turbocharger compressor bypass system consists of the following components:
Turbocharger Compressor Bypass Valve (TCBV) controller
Turbocharger Compressor Bypass Valve (TCBV)
Turbocharger Compressor Bypass (TCBV) absolute pressure sensorTurbocharger Compressor Bypass Valve (TCBV) Controller (A5M8)The TCBV controller receives operating voltage from the control system. The controller receives commands from the ECM for the engine via a CAN data link. The controller converts the commands from the ECM into a command signal for the TCBV. The controller also provides 5 VDC to the valve position sensor.Turbocharger Compressor Bypass Valve (TCBV)The TCBV positions an actuator according to the commands from the controller. The position sensor sends a signal to the controller. The signal indicates the position of the actuator.The TCBV controller sends the position of the actuator to the engine ECM via the CAN data link. The position of the actuator can be viewed on Caterpillar Electronic Technician (ET). The controller also sends diagnostic information to the ECM.Absolute Pressure SensorThe TCBV absolute pressure sensor converts the absolute pressure of the turbocharger compressor bypass air into an electrical signal. The ECM uses the signal to determine the volume of turbocharger compressor bypass air that is being provided. The ECM changes the command to the TCBV controller until the volume of turbocharger compressor bypass air is correct.
Table 2
Troubleshooting Test Steps Values Results
1. Determine the Diagnostic Code
A. Establish communication between Cat ET and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Record the logged codes or the active codes.
Diagnostic Code
Result: A 1720-5, 1720-6, 5005-3, 5005-4, 3482-3 or a 3482-4 code is logged or active. There is a problem with the wiring between the TCBV controller (A5M8) and the TCBV.
Proceed to Test Step 7.
Result: A 4781-3, 4781-4, 4781-5 or a 4781-6 code is logged or active. There is a problem with the power supply to the TCBV controller (A5M8).
Proceed to Test Step 10.
Result: A 1720–7 code is logged or active.
Proceed to Test Step 2.
Result: A 1720–8 code is logged or active.
Clear all logged or active codes and Proceed to Test Step 6.
Illustration 1 g06139675
Table 3
Troubleshooting Test Steps Values Results
2. Inspect the Wiring to the Actuator
A. Inspect the wiring from the ECM to the actuator for the TCBV.
B. Check all connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect".
C. Check the wires for damage to the insulation.
D. Inspect the wires for the following conditions:
Exposed insulation
Rubbing of a wire against the engine
Rubbing of a wire against a sharp point
Perform a pull test on each wire terminal connection. Refer to Troubleshooting, "Electrical Connectors - Inspect".
Wiring
Result: A damaged wire or damaged connector was not found.
Proceed to Test Step 3.
Result: A damaged wire or damaged connector was found.
Repair: Repair the damaged wire or the damaged connector. Proceed to Test Step 3.
3. Perform the "Turbocharger Compressor Bypass Valve Test"
A. Perform the "Turbocharger Compressor Bypass Valve Test" in Cat ET.