13A-IGNITION SWITCH - ST SYSTEM AND STARTER RELAY SYSTEM<M/T>

Inspection procedure 24: Ignition switch-ST system and starter relay system <M/T>

CIRCUIT OPERATION

If the clutch interlock switch is ON (when the clutch pedal is depressed.) and the ignition switch is turned to "START" position, battery positive voltage is supplied to starter relay coil. With this, the starter relay turns "ON" the battery positive voltage is supplied to the starter motor terminal from the battery.

COMMENT

Faulty starting system and the related circuit are suspected to be the causes.

TROUBLESHOOTING HINTS (The most likely causes for this case:)

Battery failed.
Ignition switch failed. <Vehicles without KOS>
OSS-ECU failed. <Vehicles with KOS>
Starter relay failed.
Starter motor failed.
Open or shorted starting system circuit, harness damage or connector damage.
Clutch interlock switch failed.
ECM failed.

DIAGNOSIS

Required Special Tools:

MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
MB992745: V.C.I.-Lite main harness A
MB992747: V.C.I.-Lite USB cable short
MB992748: V.C.I.-Lite USB cable long
MB991958: Scan Tool (M.U.T.-III Sub Assembly)

MB991824: Vehicles Communication Interface (V.C.I.)
MB991827: M.U.T.-III USB Cable
MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool (M.U.T.-III), check data list item 79: Cranking Signal.

(1)

caution

To prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).

Connect scan tool (M.U.T-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III)

(2) Turn the ignition switch to the "ON" position.

(3) Set scan tool (M.U.T-III) to the data reading mode for item 79, Cranking Signal.

When the engine is stopped, "OFF" should be displayed.
When the engine is cranked, "ON" should be displayed.

(4) Turn the ignition switch to the "LOCK" (OFF) position.

Is the operating properly?

Go to Step 8

Go to Step 2

STEP 2. Measure the ignition switch-ST signal voltage at ECM harness side connector.

(1) Disconnect the connector and measure at the harness side.

(2) Turn the ignition switch to the "START" position.

(3) Measure the voltage between terminal ST line and ground.

Voltage should be battery positive voltage.

(4) Turn the ignition switch to the "LOCK" (OFF) position.

Is battery positive voltage (approximately 12 volts) present?

Go to Step 5

. <Vehicles without KOS>

Go to Step 6

. <Vehicles with KOS>

Go to Step 3

. <Vehicles without KOS>

Go to Step 4

. <Vehicles with KOS>

STEP 3. Check the ignition switch.

Refer to GROUP 54A, Ignition Switch - Inspection - Ignition Switch Continuity Check

Are there any abnormalities?

Replace the ignition switch. Then confirm that the malfunction symptom is eliminated.

Repair or replace the connector(s), or check and repair the harness of open circuit, and short to ground in ST line between ignition switch connector and ECM connector. Then confirm that the malfunction symptom is eliminated.

STEP 4. Check of open circuit and short circuit to ground in ST line between OSS-ECU connector and ETACS-ECU connector.

Is the harness wire in good condition?

Perform troubleshooting of OSS System (Refer to GROUP 42B - Troubleshooting - Trouble Symptom Chart

Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.

STEP 5. Check of harness damage in ST line between ignition switch connector and ECM connector.

Is the harness wire in good condition?

Go to Step 7

Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.

STEP 6. Check of harness damage in ST line between OSS-ECU connector and ECM connector.

Is the harness wire in good condition?

Go to Step 7

Repair it. Then confirm that the malfunction symptom is eliminated.

STEP 7. Using scan tool (M.U.T.-III), check data list item 79: Cranking Signal.

(1) Turn the ignition switch to the "ON" position.

(2) Set scan tool (M.U.T.-III) to the data reading mode for item 79, Cranking Signal.

When the engine is stopped, "OFF" should be displayed.
When the engine is cranked, "ON" should be displayed.

(3) Turn the ignition switch to the "LOCK" (OFF) position.

Is the operating properly?

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions

Replace the ECM (Refer to, Removal and Installation

). Then confirm that the malfunction symptom is eliminated.

STEP 8. Check the starter relay.

(1) Remove the starter relay.

(2) Check for continuity between the starter relay coil terminals.

There should be continuity.

(3) Use jumper wires to connect starter relay terminal STRL line side to the positive battery terminal and terminal ground line side to the negative battery terminal.

(4) Check for continuity between the starter relay switch side terminals while connecting and disconnecting the jumper wire at the negative battery terminal.

Continuity (2 ohms or less). <Negative battery terminal connected>
Should be open loop. <Negative battery terminal disconnected>

(5) Install the starter relay.

Is the measured resistance normal?

Go to Step 9

Replace the starter relay. Then confirm that the malfunction symptom is eliminated.

STEP 9. Check the continuity at starter relay harness side connector.

(1) Disconnect the starter relay connector and measure at the harness side.

(2) Check for the continuity between terminal coil ground line and ground.

Continuity (2 ohms or less).

Does continuity exist?

Go to Step 10

Repair or replace the connector(s), or check and repair the harness of open circuit and harness damage in coil ground line between starter relay connector and body ground. Then confirm that the malfunction symptom is eliminated.

STEP 10. Measure the power supply voltage at starter relay harness side connector.

(1) Disconnect the starter relay connector and measure at the harness side.

(2) The clutch pedal is depressed.

(3) Turn the ignition switch to the "START" position.

(4) Measure the voltage between terminal STRL line and ground.

Voltage should be battery positive voltage.

(5) Turn the ignition switch to the "LOCK" (OFF) position.

Is battery positive voltage (approximately 12 volts) present?

Go to Step 15

Go to Step 11

STEP 11. Check the clutch interlock switch.

Refer to GROUP 21A, On-vehicle Servicer - Interlock Switch Check and Adjustment

Is the clutch interlock switch normal?

Go to Step 12

Replace the clutch interlock switch. Then confirm that the malfunction symptom is eliminated.

STEP 12. Measure the power supply voltage at clutch interlock switch harness side connector.

(1) Disconnect the clutch interlock switch connector and measure at the harness side.

(2) Turn the ignition switch to the "START" position.

(3) Measure the voltage between terminal STRL line and ground.

Voltage should be battery positive voltage.

(4) Turn the ignition switch to the "LOCK" (OFF) position.

Is battery positive voltage (approximately 12 volts) present?

Repair or replace the connector(s), or check and repair the harness of open circuit, and short to ground in power supply line between clutch interlock relay and starter relay. Then confirm that the malfunction symptom is eliminated.

Go to Step 13

STEP 13. Check of open circuit and short circuit to ground in STRL line between ECM connector and clutch interlock switch connector.

Is the harness wire in good condition?

Go to Step 14

Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.

STEP 14. Using scan tool (M.U.T.-III), check data list item 102: Starter Relay.

(1) Turn the ignition switch to the "ON" position.

(2) Set scan tool (M.U.T.-III) to the data reading mode for item 102, Starter Relay.

When the engine is stopped, "OFF" should be displayed.
When the engine is cranked, "ON" should be displayed.

(3) Turn the ignition switch to the "LOCK" (OFF) position.

Is the operating properly?

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions

Replace the ECM (Refer to, Removal and Installation

). Then confirm that the malfunction symptom is eliminated.

STEP 15. Measure the power supply voltage at starter harness side connector.

(1) Disconnect the starter motor magnetic switch connector and measure at the harness side.

(2) Turn the ignition switch to the "START" position.

(3) Measure the voltage between terminal starter relay output line and ground.

Voltage should be battery positive voltage.

(4) Turn the ignition switch to the "LOCK" (OFF) position.

Is battery positive voltage (approximately 12 volts) present?

Go to Step 20

Go to Step 16

STEP 16. Measure the power supply voltage at starter relay harness side connector.

(1) Disconnect the starter relay connector and measure at the harness side.

(2) Measure the voltage between terminal battery line and ground.

Voltage should be battery positive voltage.

Is battery positive voltage (approximately 12 volts) present?

Go to Step 17

Repair or replace the connector(s), or check and repair the harness of open circuit, and short to ground in power supply line between fusible link and starter relay connector. Then confirm that the malfunction symptom is eliminated.

STEP 17. Check of open circuit and short circuit to ground in starter relay output line between starter relay connector and starter connector.

Is the harness wire in good condition?

Go to Step 18

Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.

STEP 18. Check of short circuit to ground in STCD line between starter relay connector and ECM connector.

Is the harness wire in good condition?

Go to Step 19

Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.

STEP 19. Check of harness damage in STRL line between ECM connector and clutch interlock switch connector.

Is the harness wire in good condition?

Repair or replace the connector(s), or check and repair the harness of damage in power supply line between clutch interlock switch connector and starter relay connector. Then confirm that the malfunction symptom is eliminated.

Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.

STEP 20. Check of harness damage in output line between starter relay connector and starter connector.

Is the harness wire in good condition?

Go to Step 21

Repair it. Then confirm that the malfunction symptom is eliminated.

STEP 21. Check of harness damage in power supply line between fusible link and starter relay connector.

Is the harness wire in good condition?

Go to Step 22

Repair it. Then confirm that the malfunction symptom is eliminated.

STEP 22. Check of open circuit, short circuit to ground and harness damage in battery line between battery and starter connector.

Is the harness wire in good condition?

Replace the starter. Then confirm that the malfunction symptom is eliminated.

Repair it. Then confirm that the malfunction symptom is eliminated.