Diagnose and fix Subaru P0851 or P0852
Subaru has issued a service bulletin #16-68-06 to address a Subaru P0851 trouble code on the vehicles listed below. You may also see a P0852 in conjunction with the P0851. The fix is to adjust the inhibitor switch and select cable
P0851 (Neutral Switch Input Circuit Low)
P0852 (Neutral Switch Input Circuit High).
Subaru states that if you find either of these trouble codes, start by adjusting the inhibitor switch and the select cable.
Adjust Subaru inhibitor switch — Step-by-step instructions
1) Set the shifter to the “N” range.
2) Loosen the three inhibitor switch securing bolts.
3) Insert ST (special tool) 499267300 Stopper Pin as vertical as possible into the holes in the inhibitor switch lever and switch body.
4) Tighten the 3 inhibitor switch bolts to 2.5 ft/lbs. and then remove the special tool
Vehicles affected by Subaru service bulletin #16-68-06
Vehicles Equipped with 4EAT transmission
Adjustment Subaru select cable — Step-by-step
1) Place shifter in the “N” range
2) Then loosen the adjusting nuts A and B as shown in the diagram.
3) Turn the adjusting nut B until it lightly touches the connector C
3) Then hold nut B so that it does not rotate while tightening adjusting nut A. Tighten adjusting nut A to 5.5 ft-lb.
4) Confirm that the select lever operates normally:
• Move the select lever from “P” to “D” range. Check that the detents could be felt in each range. If the detents cannot be felt or the position pointer (dash indicator) is improperly aligned, re-adjust the cable.
• Check if the starter motor operates when the select lever is set to “P” range.
• Check the back-up light illumination when the select lever is in “R” range.
• Check the parking lock operation when the select lever is in “P” range.
5) Using a scan tool, clear the diagnostic trouble codes. If the codes return after the correct adjustments follow these diagnostic steps.
Test Subaru Inhibitor Switch Auto Transmission
Refer to Inhibitor switch and Neutral switch testing procedures in a shop manual to test for voltage and resistance to rule out short to ground, excessive resistance, faulty inhibitor switch.
©, 2020 Rick Muscoplat