New Holland ENG 187 – ENGINE: Sensor Supply 2 Voltage is too low

The Engine Control Module (ECM) provides a 5-volt reference signal to a specific network of sensors on the engine harness. This code triggers when the ECM detects that the voltage on the Sensor Supply 2 circuit has dropped below the minimum acceptable range. This voltage drop is typically caused by a short circuit to ground in the wiring harness, a short between a supply and return line, an internally shorted sensor pulling the voltage down, or an internal failure of the ECM's power supply.

• New Holland T8000 Series Tractors
• New Holland T7 Series Tractors
• New Holland CR9090 Combines
• New Holland CX8080 Elevation Combines
• New Holland CX8090 Elevation Combines

1. 1

   Consult the specific machine's wiring diagram to identify all sensors powered by the "Sensor Supply 2" circuit. Depending on the exact engine, this often includes UREA pressure sensors, fuel rail pressure sensors, or accelerator pedal position sensors.

2. 2

   Always inspect connectors before replacing sensors. Look for dirt, moisture, corrosion, or bent pins that could bridge the 5V supply to a ground wire.

3. 3

   Because multiple sensors share this 5V supply, one internally shorted sensor will pull the entire network down. With the fault code active, unplug each sensor on the Sensor Supply 2 circuit one at a time.

4. 4

   Measure the voltage directly at the ECU's Sensor Supply 2 output pin (e.g., Pin 47 on the P2 connector for some Cummins-based ECMs, or Pin 14 on ECU engine connector 2 for some FPT engines). It should read 5 VDC.

1. 1

   Verify fault code is active

   Turn the keyswitch to the ON position (engine off) and connect your diagnostic tool (e.g., CNH EST) to verify ENG 187 is currently active.

2. 2

   Disconnect sensors

   Disconnect the sensors on the Sensor Supply 2 circuit one by one.

3. 3

   Monitor fault code status

   Monitor the fault code status. If the code changes to INACTIVE immediately after a specific sensor is disconnected, that sensor has an internal short and must be replaced.

4. 4

   Disconnect engine sensor harness

   If the code remains active with all sensors disconnected, disconnect the engine sensor harness directly from the ECU.

5. 5

   Measure voltage at ECU

   Turn the keyswitch ON and measure the voltage at the ECU's Sensor Supply 2 pin.

6. 6

   Check for short to ground in wiring harness

   If the ECU outputs 5 volts with the harness disconnected, the wiring harness has a short to ground. Locate the chafed/shorted wire and repair it, or replace the engine wiring harness.

7. 7

   Check ECU for internal hardware failure

   If the ECU does not output 5 volts (reads 0V) with the harness disconnected, the ECU has an internal hardware failure and must be replaced.

8. 8

   Validate the repair

   Reconnect all components. To validate the repair, perform a key cycle, start the engine, and let it idle for 1 minute. The fault code status should change to INACTIVE, and you can clear the code from the module's history.