Engine-Codes - Pontiac - P0851 Pontiac

P0851 Pontiac Code - Park/Neutral Position Switch Circuit Low Voltage

- Code Popularity: 2,248 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 2/3
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What are the Possible Causes of the DTC P0851 Pontiac?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Park/Neutral Switch
  • Park/Neutral Switch harness is open or shorted
  • Park/Neutral Switch circuit poor electrical connection
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How to Fix the DTC P0851 Pontiac?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P0851 Pontiac code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

What Does the P0851 Pontiac Code Mean?

The transmission manual shift shaft switch assembly, also known as the Internal Mode Switch (IMS), is a sliding contact switch attached to the manual shift shaft inside the transmission case. The Park/Neutral Position (PNP) Switch is integrated into the IMS and connects to the Transmission Control Module (TCM) lead-frame through a short wire harness. The 5 inputs to the TCM from the transmission manual shift shaft switch assembly indicate the transmission gear selector lever position. This information is used for engine start enable, engine controls as well as determining the transmission shift patterns. The state of each input is available for display on the scan tool. The five input parameters represented are Signal A, Signal B, Signal C, Signal P (Parity), and Signal N (Park/Neutral Start Signal). Park/Neutral Signal is sent from the Park/Neutral switch directly to the Engine Control Module (ECM) and is used for engine start enable. The Park/Neutral Signal circuit is not connected to the TCM internally; the circuit uses the TCM as a pass-through connector only. The ECM Park/Neutral diagnostic monitors the Park/Neutral Signal circuit to detect Low voltage when the ECM expects to see High voltage and High voltage when the ECM expects to see Low voltage.

P0851 Pontiac Code - Park/Neutral Position Switch Circuit Low Voltage

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