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2008 - MX-5 - Engine

DTC P0850 [LF]



DTC P0850

Neutral switch input circuit problem

DETECTION CONDITION

  • The PCM monitors changes in input voltage from the neutral switch. If the PCM does not detect the voltage changes while driving the vehicle at a vehicle speed above 30 km/h {19 mph} and clutch pedal turns press and depress 10 times repeatedly, the PCM determines that the neutral switch circuit has a malfunction

    Diagnostic support note
  • This is a continuous monitor (CCM).

  • The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.

  • PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.

  • FREEZE FRAME DATA is available.

  • The DTC is stored in the PCM memory.

POSSIBLE CAUSE

  • Neutral switch malfunction

  • Poor connection of neutral switch connector or PCM connector

  • Short to ground in wiring harness between neutral switch terminal 2A and PCM terminal 1X

  • Open circuit in wiring harness between neutral switch terminal 2A and PCM terminal 1X

  • Open circuit in wiring harness between ground and neutral switch terminal 1A

  • PCM malfunction


Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA HAS BEEN RECORDED
  • Has FREEZE FRAME DATA been recorded?

Yes

Go to the next step.

No

Record the FREEZE FRAME DATA on the repair order, then go to the next step.

2

VERIFY RELATED REPAIR INFORMATION AVAILABILITY
  • Verify related Service Bulletins and/or on-line repair information availability.

  • Is any related repair information available?

Yes

Perform repair or diagnosis according to the available repair information.

  • If the vehicle is not repaired, go to the next step.

No

Go to the next step.

3

CLASSIFY HIGH INPUT OR LOW INPUT
  • Connect the M-MDS to DLC‐2.

  • Access CPP/PNP PID.

  • Verify CPP/PNP PID when gear is neutral position.

  • Is CPP/PNP PID always off?

Yes

Go to the next step.

No

Go to Step 10.

4

INSPECT NEUTRAL SWITCH CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect neutral switch connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 14.

No

Go to the next step.

5

CLASSIFY NEUTRAL SWITCH OR CIRCUIT
  • Connect the M-MDS to the DLC‐2.

  • Access CPP/PNP PID.

  • Connect a jumper wire between neutral switch terminal 1A and 2A.

  • Is CPP/PNP PID on?

Yes

Go to the next step.

No

Go to Step 7.

6

INSPECT NEUTRAL SWITCH

Yes

Go to Step 14.

No

Replace the neutral switch, then go to Step 14.

7

INSPECT NEUTRAL SWITCH GROUND CIRCUIT FOR OPEN CIRCUIT
  • Inspect for continuity between neutral switch terminal 1A and ground.

  • Is there continuity?

Yes

Go to the next step.

No

Repair or replace the neutral switch ground circuit for an open circuit, then Go to Step 14.

8

INSPECT PCM CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect the PCM connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 14.

No

Go to the next step.

9

INSPECT NEUTRAL SWITCH SIGNAL CIRCUIT FOR OPEN CIRCUIT
  • Inspect for continuity between neutral switch terminal 2A and PCM terminal 1X.

  • Is there continuity?

Yes

Repair or replace the wiring harness for an open circuit, then go to Step 14.

No

Go to Step 14.

10

INSPECT NEUTRAL SWITCH CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect the neutral switch connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 14.

No

Go to the next step.

11

CLASSIFY NEUTRAL SWITCH OR CIRCUIT
  • Connect the M-MDS to DLC‐2.

  • Access CPP/PNP PID.

  • Verify that CPP/PNP PID changes from ON to OFF when the neutral switch connector disconnected.

  • Does CPP/PNP PID change from ON to OFF?

Yes

Go to the next step.

No

Go to Step 13.

12

INSPECT NEUTRAL SWITCH

Yes

Go to Step 14.

No

Replace the neutral switch, then go to Step 14.

13

INSPECT NEUTRAL SWITCH SIGNAL CIRCUIT FOR SHORT TO GROUND
  • Inspect for continuity between neutral switch terminal 2A and ground.

  • Is there continuity?

Yes

Repair or replace the wiring harness for short to ground, then go to the next step.

No

Go to the next step.

14

VERIFY TROUBLESHOOTING OF DTC P0850 COMPLETED
  • Make sure to reconnect all disconnected connectors.

  • Start the engine.

  • Clear the DTC from the PCM memory using the M-MDS.

  • Drive the vehicle above 30 km/h {19 mph} and stop vehicle.

  • Depress and release the clutch pedal more than 10 times during drive cycle.

  • Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

15

VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC troubleshooting.

(See DTC TABLE [LF].)

No

Troubleshooting completed.




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