P0850

P0850-P/N SWITCH PERFORMANCE (DIESEL)





For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams


- When Monitored:

Continuously with the ignition on and engine running.

- Set Condition:

The Transmission governor pressure set point is above a threshold while in park or the P/N switch is in drive during an engine start.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Checkout (Diesel)



Diagnostic Test


1. CHECK IF THE SCAN TOOL DISPLAYS P/N AND D/R IN THE CORRECT POSITION

Ignition on, engine not running.

With the scan tool, monitor the PNP switch input state.

Move the gear selector through all gear positions Park to 1st and back to Park.

Did the scan tool display P/N and D/R in the correct gear positions?

Yes

- Go To 8

No

- Go To 2



2. CHECK THE TRS CONNECTOR FOR DAMAGE OR CORROSION

Turn the ignition off to the lock position.

Disconnect the Transmission Range Sensor harness connector.

Inspect the Transmission Range Sensor harness wiring and connector for damage, pushed out pins, or corrosion, etc.

Were there any problems found?

Yes

- Repair as necessary.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Go To 3



3. CHECK THE ECM CONNECTOR FOR DAMAGE OR CORROSION

Disconnect the ECM C2 harness connector.

Inspect the ECM wiring and connector for damage, pushed out pins, or corrosion, etc.

Were there any problems found?

Yes

- Repair as necessary.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Go To 4



4. CHECK THE (T41) P/N POSITION SWITCH SENSE CIRCUIT FOR AN OPEN





Measure the resistance of the (T41) P/N Position Switch Sense circuit between the ECM C2 harness connector and the Transmission Range Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 5

No

- Repair the (T41) P/N Position Switch Sense circuit for an open.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



5. CHECK THE (T41) P/N POSITION SWITCH SENSE CIRCUIT FOR A SHORT TO GROUND





Measure the resistance between ground and the (T41) P/N Position Switch Sense circuit.

Is the resistance greater then 100k ohms?

Yes

- Go To 6

No

- Repair the (T41) P/N Position Switch Sense circuit for a short to ground.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



6. CHECK THE (T41) P/N POSITION SWITCH SENSE CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT





Measure the resistance between the (T41) P/N Position Switch Sense circuit and all other circuits in the ECM C1 and C2 harness connectors.

Is the resistance greater 100k ohms between the (T41) P/N Position Switch Sense circuit and any other circuit(s) in the ECM C1 and C2 harness connectors?

Yes

- Go To 7

No

- Repair the (T41) P/N Position Switch Sense circuit for a short to another circuit(s).
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



7. CHECK THE TRANSMISSION RANGE SENSOR





Reconnect the Transmission Range Sensor harness connector.

Move the gear selector through all gear positions, from Park to 1st and back.

While moving the gear selector through the gear positions, measure the resistance between ground and the (T41) P/N Position Switch Sense circuit in the ECM harness connector.


NOTE: The circuit is grounded in Park and Neutral and open in the other positions.

Did the display change from above 100k ohms (open) to below 5.0 ohms (grounded)?

Yes

- Using the schematics as a guide, check the Engine Control Module (ECM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the ECM.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Replace the Transmission Range Sensor.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



8. INTERMITTENT WIRING AND CONNECTORS

The conditions necessary to set this DTC are not present at this time.

Use the Freeze Frame Data to help duplicate the conditions in which the DTC originally set. Pay particular attention to the DTC set conditions, such as, VSS, MAP, ECT, and Load

Using the schematics as a guide, visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.

Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.

Wiggle the wiring and connectors while checking for any possible open or shorted circuits.

Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Test Complete.