13A-IGNITION SWITCH

Inspection procedure 25: Ignition switch-ST system and starter relay system

CIRCUIT OPERATION

If the selector lever is moved to "P" or "N" range 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 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.
Transmission range 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 ETACS-ECU harness side connector.

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

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

(3) Measure the voltage between terminal ST 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.

: Go to Step 6.

: Go to Step 3.

: Go to Step 4.

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 short to ground and open circuit in ST line between ignition switch connector and ETACS-ECU connector. Then confirm that the malfunction symptom is eliminated.

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

Is the harness wire in good condition?

Check the OSS System. Refer to GROUP 42B, Diagnosis <OSS-ECU> - 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 ETACS-ECU 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 ETACS-ECU 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 7. Check the continuity at ETACS-ECU side connectors.

(1) Disconnect the ETACS-ECU connector and measure at the ETACS-ECU side.

(2) Check for the continuity between terminal ST and ST2.

Continuity (2 ohms or less).

Does continuity exist?

Repair or replace the connector(s), or check and repair the harness of short to ground, open circuit and harness damage in ST2 line between ETACS-ECU connector and ECM connector. Then confirm that the malfunction symptom is eliminated.

Replace the ETACS-ECU. 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 to the positive battery terminal and terminal ground line to the negative battery terminal.

(4) Check for continuity between the starter relay switch 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 for 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 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) Transmission: P or N range

(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 transmission range switch.

Refer to GROUP 23A, On-vehicle Service - Essential Service - Transmission Range Switch Continuity Check

Are there any abnormalities?

Replace the transmission range switch. Then confirm that the malfunction symptom is eliminated.

Go to Step 12.

STEP 12. Measure the power supply voltage at transmission range switch harness side connector.

(1) Disconnect the transmission range 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?

Go to Step 14.

Go to Step 13.

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

Is the harness wire in good condition?

Replace the ECM (Refer to Removal and Installation

). Then confirm that the malfunction symptom is eliminated.

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

STEP 14. Check of short to ground and open circuit in power supply line between transmission range switch connector and starter relay.

Is the harness wire in good condition?

Repair or replace the connector(s), or check and repair the harness of short circuit to ground in NTSW line between starter relay connector and ECM 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 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 side power supply 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 19.

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 side power supply 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 short to ground and open circuit in power supply line between fusible link and starter relay connector. Then confirm that the malfunction symptom is eliminated.

STEP 17. Check of short to ground and open circuit in power supply 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 harness damage in STRL line between ECM connector and transmission range 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 transmission range 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 19. Check of harness damage in power supply line between starter relay connector and starter connector.

Is the harness wire in good condition?

Go to Step 20.

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

STEP 20. 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 21.

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

STEP 21. Check of short to ground, open circuit and harness damage in power supply 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 the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.