John Deere 177.03 – CCU, EPC, PTP, BIF, or TCU: Transmission Oil Temperature Sensor Voltage Too High

The control unit has detected that the voltage at the signal input of the transmission oil temperature sensor (often designated as lead 6002) is too high. The system interprets this high voltage as a temperature value below 34°C (29°F), which typically indicates that the sensor's circuit is either open or shorted to a positive lead (power).

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6010–6910 series
• 6120–6420 series
• 6090MC/RC to 6110MC/RC
• 9230–9630 articulated tractors
• 450J
• 550J
• 650J
• 750J
• 850J
• 310J
• 310K
• 325J
• 410J
• 710J
• 540G-III
• 548G-III

1. 1

   Inspect Sensor Wiring: Check the wiring harness leading to the transmission oil temperature sensor for any signs of chafing, severed wires (open circuit), or wires melted/rubbing against a power source (short to power).

2. 2

   Verify Connections: Disconnect the sensor and ensure the connector terminals are secure, tight, and free of water ingress or corrosion.

3. 3

   Test Voltage: Turn the key to the ON position. Measure the voltage at the signal input of the harness connector to confirm if it is receiving the correct reference voltage (usually 5V) or if it is shorted to battery voltage.

4. 4

   Test Sensor Resistance: Remove the sensor from the circuit and test its resistance with a multimeter. (For example, on some 6000-series tractors, a healthy B60 sensor should read roughly 979 Ohms at 50°C / 122°F. An infinite reading indicates an internally open/failed sensor).

1. 1

   Power Down

   Turn the machine off and engage the parking brake. Turn the key switch to the ON position (engine off) to verify the code is active, then turn it back OFF.

2. 2

   Locate the Sensor

   Locate the transmission oil temperature sensor (B60) on the transmission housing.

3. 3

   Disconnect and Inspect

   Unplug the sensor harness. Clean the connector with electrical contact cleaner if dirt or oil is present.

4. 4

   Harness Repair (If Applicable)

   If your multimeter testing revealed a short to power or a broken wire in the harness, trace the lead (wire 6002) back to the control module and splice/repair the damaged section.

5. 5

   Replace the Sensor

   If the wiring tests good, the sensor has failed internally. Unthread the old sensor from the transmission housing (have a catch pan ready for minor oil loss).

6. 6

   Install New Sensor

   Thread the new sensor in, taking care not to overtighten. Reconnect the wiring harness.

7. 7

   Clear and Test

   Turn the key ON, clear the stored fault codes via the monitor, and start the machine. Monitor the transmission oil temperature readings to ensure they are accurate and that code 000177.03 does not return.