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DTC P0850:24 [START STOP UNIT]

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2016 – MX-5 – Body and Accessories

DTC P0850:24 [START STOP UNIT]

Description

Transmission range switch circuit malfunction

Detection condition

  • The start stop unit detected the following condition 5 times continuously with the ignition switched ON (engine off or on).

    • Transmission range switch is stuck off for a continuous 1 s or more even though the TCM CAN signal is in a position the P or N position.

Fail-safe

  • Perform control of the internal signal for control of the transmission range switch as position other than P, N positions.

Possible cause

  • DTCs are stored in the TCM.

  • Transmission range switch connector or terminal malfunction

  • Open circuit in wiring harness between transmission range switch terminal A and body ground

  • PCM connector or terminal malfunction

  • Start stop unit connector or terminal malfunction

  • Open circuit in wiring harness between the following terminals:

    • PCM terminal 2BD—Transmission range switch terminal I

    • Start stop unit terminal 1F—Transmission range switch terminal I

  • Transmission range switch malfunction

  • PCM malfunction

  • Start stop unit malfunction

Diagnostic Procedure

Step

Inspection

Action

1

VERIFY TCM DTCs

Yes

Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.

(See ON-BOARD DIAGNOSTIC SYSTEM DTC TABLE [TCM (SJ6A-EL)].)

No

Go to the next step.

2

INSPECT TRANSMISSION RANGE SWITCH CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Disconnect the transmission range switch connector.

  • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.

  • Is the connector normal?

Yes

Go to the next step.

No

Repair or replace the connector, then go to Step 9.

3

INSPECT TRANSMISSION RANGE SWITCH GROUND CIRCUIT FOR OPEN CIRCUIT

  • Verify that the transmission range switch connector is disconnected.

  • Inspect for continuity between transmission range switch terminal A (wiring harness-side) and body ground.

  • Is there continuity?

Yes

Go to the next step.

No

Refer to the wiring diagram and verify whether or not there is a common connector between transmission range switch terminal A and body ground.

    If there is a common connector:

  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.

  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has an open circuit.

Go to Step 9.

4

INSPECT PCM CONNECTOR CONDITION

  • Disconnect the PCM connector.

  • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.

  • Is the connector normal?

Yes

Go to the next step.

No

Repair or replace the connector, then go to Step 9.

5

INSPECT START STOP UNIT CONNECTOR CONDITION

  • Disconnect the start stop unit connector.

  • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.

  • Is the connector normal?

Yes

Go to the next step.

No

Repair or replace the connector, then go to Step 9.

6

INSPECT TRANSMISSION RANGE SWITCH CIRCUIT FOR OPEN CIRCUIT

  • Verify that the start stop unit, PCM and transmission range switch connectors are disconnected.

  • Inspect for continuity between the following terminals (wiring harness-side):

    • PCM terminal 2BD—Transmission range switch terminal I

    • Start stop unit terminal 1F—Transmission range switch terminal I

  • Is there continuity?

Yes

Go to the next step.

No

Refer to the wiring diagram and verify whether or not there is a common connector between the following terminals:

  • PCM terminal 2BD—Transmission range switch terminal I

  • Start stop unit terminal 1F—Transmission range switch terminal I

    If there is a common connector:

  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.

  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has an open circuit.

Go to Step 9.

7

INSPECT TRANSMISSION RANGE SWITCH

Yes

Go to the next step.

No

Replace the transmission range switch, then go to Step 9.

(See TRANSMISSION RANGE (TR) SWITCH REMOVAL/INSTALLATION [SJ6A-EL].)

8

VERIFY IF MALFUNCTIONING LOCATION IS PCM DEPENDING ON REPEATABILITY

  • Always reconnect all disconnected connectors.

  • Connect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Clear the DTC for the start stop unit using the M-MDS.

    (See CLEARING DTC [START STOP UNIT].)

  • Switch the ignition ON (engine off).

  • Perform the following work 5 times or more.

    • Operate the selector lever to P or N position and wait for 1 s or more.

    • Operate the selector lever to other than P and N position and wait for 1 s or more.

    • Operate the selector lever to P or N position.

  • Retrieve the start stop unit DTCs using the M-MDS.

    (See DTC INSPECTION [START STOP UNIT].)

  • Is the same DTC displayed?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

No

Go to Step 10.

9

VERIFY THAT REPAIRS HAVE BEEN COMPLETED

  • Always reconnect all disconnected connectors.

  • Connect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Clear the DTC for the start stop unit using the M-MDS.

    (See CLEARING DTC [START STOP UNIT].)

  • Switch the ignition ON (engine off).

  • Perform the following work 5 times or more.

    • Operate the selector lever to P or N position and wait for 1 s or more.

    • Operate the selector lever to other than P and N position and wait for 1 s or more.

    • Operate the selector lever to P or N position.

  • Retrieve the start stop unit DTCs using the M-MDS.

    (See DTC INSPECTION [START STOP UNIT].)

  • Is the same DTC displayed?

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

10

VERIFY IF OTHER DTCs DISPLAYED

  • Are any other DTCs displayed?

Yes

Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.

(See DTC TABLE [START STOP UNIT].)

No

DTC troubleshooting completed.

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