858891T 3 Mercury ECU, Engine Control Unit

Table 1
Diagnostic Trouble Codes    
Code and Description    Conditions that Generate the Code    System Response    
172-3 Engine Intercooler Temperature : Voltage Above Normal     The ECM detects signal voltage that is above normal for one second.
The ECM has been powered for at least 3 seconds     The code is logged.    
172-4 Engine Intercooler Temperature : Voltage Below Normal     The ECM detects signal voltage that is below normal for one second.
The ECM has been powered for at least 3 seconds    System OperationUse this procedure to troubleshoot any suspect problems with the following sensors for the primary ECM:
Intake manifold air temperature sensor
Illustration 1 g03352710
Typical primary schematic
Illustration 2 g03352711
Terminal locations at the P1 ECM connector for the passive sensor (P1-14) Inlet manifold air temperature (P1-3) Sensor return
Illustration 3 g01155187
Terminal locations at the connector for the passive analog sensors (Terminal 1) Sensor signal (Terminal 2) Sensor return
Table 2
Troubleshooting Test Steps    Values    Results    
1. Check for "Active" or "Logged" Diagnostic Codes
A. Connect Caterpillar Electronic Technician (ET) to the service tool connector.
B. Restore the electrical power to the ECM.
C. Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
D. Determine if the problem is active and related to one of the following diagnostic codes:
-3
-4    
Codes    
Results: No diagnostic codes are active at this time.
Repair: The problem may be intermittent. If the problem is intermittent refer to Troubleshooting, "Electrical Connectors - Inspect"
Results: An active -3 diagnostic code is present.
Proceed to Test Step 2
Results: An active -4 diagnostic code is present.
Proceed to Test Step 4
   
2. Check for a Short to the +Battery at the Sensor Connector
A. Measure the voltage on the harness side of the sensor connector between pin 1 and pin 2 for the suspect sensor.
   
+Battery    
Results: The supply voltage is less than Battery voltage.
Proceed to Test Step 3
Results: The supply voltage is equal to Battery voltage.
Repair: There is a short in the harness to the +Battery. Repair the wiring.
Verify that the repair eliminated the problem.    
3. Create a Short at the Sensor Connector
A. Turn the main disconnect switch to the OFF position.
B. Disconnect the suspect sensor.
C. Use a wire jumper in order to create a short between terminal 1 (signal) and terminal 2 (sensor return) at the sensor connector.
D. Restore the electrical power to the ECM.
E. Access the "Active Diagnostic Code" screen on Cat ET. Check for an active -4 diagnostic code for the suspect sensor.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
F. Turn the main disconnect switch to the OFF position.    
Short    
Results: A -3 diagnostic code was active before creating the short at the sensor connector. A -4 diagnostic code became active after creating the short at the sensor connector.
Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.
Verify that the repair eliminated the problem.
Results: A -3 diagnostic code is still active for the suspect sensor.
Proceed to Test Step 5
   
4. Create an Open at the Suspect Sensor Connector
A. Disconnect the sensor connector of the suspect sensor with the active -4 diagnostic code.
B. Restore the electrical power to the ECM.
C. Access the "Active Diagnostic Code" screen on Cat ET. Check for an active -3 diagnostic code.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
D. Turn the main disconnect switch to the OFF position.
   
Open    
Results: A -4 diagnostic code was active before disconnecting the sensor. A -3 diagnostic code became active after disconnecting the sensor.
Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.
Verify that the repair eliminated the problem.
Results: A -4 diagnostic code is still active for the suspect sensor. There is a short circuit between the sensor connector and the ECM. Leave the sensor disconnected.
Proceed to Test Step 5    
5. Check the Operation of the ECM
A. Check the operation of the ECM by creating an open at the ECM.
B. Remove the signal wire for the suspect sensor from the P1 ECM connector. Refer to Illustration 2 for terminal locations.
C. Fabricate a jumper wire that is long enough to create a test circuit between the ECM connector and the ECM ground strap. Crimp a connector socket to one end of the jumper wire.
E. Install the jumper wire into the terminal location of the signal wire for the suspect sensor.
F. Reconnect the ECM connectors. Ensure that the loose end of the jumper wire does not contact any ground source during the test.
G. Restore the electrical power to the ECM. Monitor the "Active Diagnostic Code" screen on Cat ET. An open circuit diagnostic code -3 should be active for the suspect sensor.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
H. Check the operation of the ECM by creating a short at the ECM.
I. Connect the loose end of the wire jumper to the ECM ground strap.
J. Monitor the "Active Diagnostic Code" screen on Cat ET. A -4 diagnostic code should be active when the wire jumper is installed.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
K. Turn the main disconnect switch to the OFF position.
L. Remove the wire jumper. Reconnect all wires and connectors.    
ECM    
Results: One of the following conditions exists: The -3 diagnostic code is active when the sensor signal wire is disconnected. The -4 diagnostic code is active when the wire jumper is installed.
Repair: If the code is active for