12804A 1 Mercury CHOKE BEZEL

Table 1
Diagnostic Codes Table
Code Conditions which Generate this Code System Response
172-3 Intake Manifold Air Temperature Sensor : Voltage Above Normal The engine's Electronic Control Module (ECM) detects signal voltage that is more than 4.8 VDC for one second.
The ECM has been powered for at least three seconds. The code is logged.
The value of the parameter is set to zero.
172-4 Intake Manifold Air Temperature Sensor : Voltage Below Normal The ECM detects signal voltage that is less than 0.2 VDC for one second.
The ECM has been powered for at least three seconds. System OperationThe sensor signal for the passive sensor is routed from the ECM to terminal 2 of the sensor connector. The sensor return for the passive sensors is routed from the ECM to terminal 1 of the sensor connector.
Illustration 1 g01383798
Typical schematic
Illustration 2 g01234146
Location of ECM connectors
Illustration 3 g01572137
P1 ECM connector
(P1-3) Analog return
(P1-14) Intake manifold air temperature sensor
Illustration 4 g01163206
Sensor connector
(Terminal 1) Analog return
(Terminal 2) Intake manifold air temperature sensor Test Step 1. Check for "Active" or "Logged" Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the keyswitch to the ON position.
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.
Determine if a diagnostic code has occurred several times. Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a poor connection between a socket and a pin in a connector or of a poor connection between a wire and a terminal.
Determine if the problem is active and related to one of the following diagnostic codes:
-3
-4Expected Result:A diagnostic code is not active.Results:
OK - A diagnostic code is not active.Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - An active -3 diagnostic code is present. Proceed to Test Step 2.
Not OK - An active -4 diagnostic code is present. Proceed to Test Step 3.Test Step 2. Create a Short at the Suspect Sensor Connector
Turn the keyswitch to the OFF position.
Disconnect the suspect sensor.
Use a wire jumper in order to create a short between terminal 2 (signal) and terminal 1 (sensor return) at the sensor connector.
Turn the keyswitch to the ON position.
Access the "Active Diagnostic Code" screen on Cat ET. Check for an active -4 diagnostic code for the suspect sensor. Expected Result:A -4 diagnostic code is now active for the suspect sensor(s).Results:
OK - 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. The wiring between the ECM and the sensor connector is OK.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.STOP
Not OK - A -3 diagnostic code is still active for the suspect sensor(s). There is an open circuit between the sensor connector and the ECM. Leave the sensor disconnected. Proceed to Test Step 4.Test Step 3. Create an Open at the Suspect Sensor Connector
Turn the keyswitch to the OFF position.
Disconnect the sensor connector of the suspect sensor(s) with the active -4 diagnostic code.
Turn the keyswitch to the ON position. Wait at least 30 seconds for activation of the diagnostic codes.
Access the "Active Diagnostic Code" screen on Cat ET. Check for an active -3 diagnostic code. Expected Result:A -3 diagnostic code is now active for the suspect sensor(s).Results:
OK - A -4 diagnostic code was active before disconnecting the sensor. A -3 diagnostic code became active after disconnecting the sensor. The wiring between the ECM and the sensor connector is OK.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.STOP
Not OK - 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 4.Test Step 4. Check the Operation of the ECM
Turn the keyswitch to the OFF position.
Check the operation of the ECM by creating an open at the ECM.
Remove the signal wire for the suspect sensor from the P1 ECM connector. Refer to Illustration 1 for terminal locations.
Install a jumper wire with Deutsch sockets on each end into the socket for the signal wire of the suspect sensor.
Reconnect the ECM connectors.
Turn the keyswitch to the ON position.
Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code. An open circuit diagnostic code -3 should be active for the suspect sensor.
Check the operation of the ECM by creating a short at the ECM.
Install a wire jumper between the wire jumper for the signal wire for the suspect sensor and engine ground.
Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code. A -4 diagnostic code should be active when the wire jumper is installed.
Turn the keyswitch to the OFF position.
Remove the wire jumper. Reconnect all wires and connectors. Expected Result:A -3 diagnostic code is active when the sensor's signal wire is open at the ECM connector. A -4 diagnostic code is active when the sensor's signal wire is connected to engine ground.Results:
OK - The ECM is operating properly. The problem is in the wiring between the ECM and the connector for the sensor.STOP
Not OK - One of the following conditions exists: The -3 diagnostic code is not active when the sensor signal wire is disconnected. The -4 diagnostic code is not active when the wire jumper is installed.Repair: Replace the ECM. Refer