The Engine Control Module (ECM) provides nine outputs that can be used to illuminate indicator lamps. The Caterpillar Electronic Technician (ET) can be used to program each output to a specific J1/P1 terminal. Some of the outputs can be programmed to a J1939 device.
Each J1/P1 output is a high side driver or a low side driver.
High Side Driver - The ECM provides an output voltage that is approximately equal to the battery voltage in order to activate the lamp.
Low Side Driver - The ECM provides a connection to ground in order to activate the lamp.
J1939 Device - The ECM sends digital data on the J1939 data link in order to control the lamp. The data is converted to a signal for the lamp by a J1939 device that is provided by the OEM.
Table 1 provides information on the lamp outputs. There are no diagnostic codes for these outputs.
| Lamp Outputs | ||||
|---|---|---|---|---|
| Lamp | Required
or Optional |
Programming Options | ||
| Default Output Terminal | Alternative
Output Terminal |
Programmable to a J1939 Device | ||
| "Amber Warning Lamp" | Required | J1/P1:28 | None | Yes |
| "Diesel Particulate Filter" | J1/P1:31 | High Side Drivers
J1/P1:10, 11, 12, 13, 19, 20 Low Side Drivers J1/P1:29, 30, 31 "J1939 - Body Controller" "J1939 - Cab Controller" "J1939 - Instrument Cluster" "J1939 - Cab Display" |
||
| "High Exhaust System Temperature" | J1/P1:30 | |||
| "Red Stop Lamp" | Optional | J1/P1:29 | ||
| "Low Oil Pressure" | None | |||
| "High Coolant Temperature" | ||||
| "Low Coolant Level" | ||||
| "Fast Idle" | No | |||
| "PTO Switch On" | ||||
| "ARD Disable Lamp" | ||||
| |
| Illustration 1 | g01350581 |
|
Examples of lamp circuits for a high side driver and a low side driver | |
| |
| Illustration 2 | g01349260 |
|
P1 terminals for the J1939 data link | |
Testing the Circuits
The ECM briefly activates the following lamps when the keyswitch is turned from OFF to ON:
- "Amber Warning Lamp"
- "Red Stop Lamp"
- "DPF Lamp"
- "High Exhaust System Temperature Lamp"
- "Aftertreatment Disable Lamp" (if equipped)
Special tests on the Caterpillar Electronic Technician (ET) can activate every lamp except the check engine lamp. The special tests activate the lamps for all programming options.
Test Step 1. Test the Circuit
If the problem is related to one of the following lamps, turn the keyswitch from OFF to ON in order to test the circuit.
- "Amber Warning Lamp"
- "Red Stop Lamp"
- "DPF Lamp"
- "High Exhaust System Temperature Lamp"
- "Aftertreatment Disable Lamp" (if equipped)
Otherwise, use the appropriate special test on Cat ET to test the circuit.
Watch the lamp during the test.
Expected Result:
The lamp does not illuminate.
Results:
- Yes - The lamp does not illuminate. Proceed to Test Step 2.
- No - The lamp illuminates.
Repair: There is a problem with the vehicle's wiring if the problem is intermittent. Troubleshoot the wiring by referring to the vehicle's wiring information.
STOP
Test Step 2. Check the Bulb
Replace the bulb with a bulb that is known to be good. Test the circuit again.
Expected Result:
The lamp illuminates.
Results:
- Yes - The lamp illuminates. The problem is resolved.
STOP
- No - The lamp does not illuminate. The bulb is OK.
Repair: The +Battery or the ground is not present at the lamp. Obtain wiring information for the vehicle.
Troubleshoot the wiring by referring to the vehicle's wiring information if the lamp output is programmed to a J1939 device.
Proceed to Test Step 3 if the lamp output is programmed to a J1/P1 terminal.
Test Step 3. Troubleshoot the Wiring for the Lamp
Check the wiring for an open circuit. Pay particular attention to possible problems with electrical connectors.
Expected Result:
There is an open circuit in the wiring for the lamp.
Results:
- Yes - There is an open circuit in the wiring for the lamp.
Repair: Make the necessary repairs.
STOP
- No - The wiring for the lamp is OK. Proceed to Test Step 4.
Test Step 4. Test the ECM Output
- Verify that the P1 connector is connected to the ECM.
- Use Cat ET to determine the programming option for the lamp output. Then, refer to Illustration 1 in order to determine if the ECM output J1/P1 terminal is a high side ECM driver or a low side ECM driver.
- Perform the following procedure if the P1 terminal is a high side driver:
Use 7X-1710 Multimeter Probes to connect a test lamp between the P1 terminal for the lamp and terminal P1-63 (−Battery).
- Perform the following procedure if the P1 terminal is a low side driver:
Use 7X-1710 Multimeter Probes to connect a test lamp between the P1 terminal for the lamp and terminal P1-53 (Unswitched +Battery).
- Test the circuit. Watch the test lamp while the output is activated.
Expected Result:
The test lamp illuminates.
Results:
- Yes - The test lamp illuminates. However, the indicator lamp does not illuminate.
Repair: Identify the cause of the vehicle's wiring problem. Make the necessary repairs.
STOP
- No - The test lamp does not illuminate. There is a problem with the ECM.
Repair: Replace the ECM.
STOP