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Inspection Procedure 28

Power Supply System And Ignition Switch-IG System.

Power Supply And Ignition Switch-IG Circuit Part 1:




Power Supply And Ignition Switch-IG Circuit Part 2:






CIRCUIT OPERATION
- Battery positive voltage is applied to the MFI relay (terminal No. 2, No. 3).
- When the ignition switch is turned to the "ON"position, the battery positive voltage is applied to the PCM (terminal No. 50).
When the battery positive voltage is applied, the PCM turns the power transistor in the PCM "ON" and grounds the MFI relay coil, with this, the MFI relay turns "ON" and the battery positive voltage is supplied to the PCM (terminal No. 34, No. 43) from the MFI relay (terminal No. 1).
- Battery positive voltage is constantly supplied to the PCM (terminal No. 58) as the backup power.
- The or PCM (terminal No. 33, No. 42) is grounded to the vehicle body.

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Malfunction of the ignition switch.
- Malfunction of the MFI relay.
- Improper connector contact, open circuit or short-circuited harness wire.
- Disconnected PCM ground wire.
- Malfunction of the PCM.

DIAGNOSIS




STEP 1. Check harness connector B-22X at MFI relay for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 2.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.

STEP 2. Check the MFI relay.




1. Remove the MFI relay.




2. Check for continuity between the MFI relay terminal No. 2 and No. 4.
- There should be continuity (approximately 70 Ohms)

3. Use jumper wires to connect MFI relay terminal No. 2 to the positive battery terminal and terminal No. 4 to the negative battery terminal.




4. Check the continuity between the MFI relay terminal No. 1 and No. 3 while connecting and disconnecting the jumper wire at the negative battery terminal.
- Should be less than 2 Ohms. (Negative battery terminal connected)
- Should be open loop. (Negative battery terminal disconnected)

5. Install the MFI relay.

Q: Is the resistance normal?

YES: Go to Step 3.

NO: Replace the MFI relay. Then confirm that the malfunction symptom is eliminated.

STEP 3. Measure the power supply voltage at MFI relay harness side connector B-22X.




1. Disconnect the connector B-22X and measure at the harness side.




2. Measure the voltage between terminal No. 2, No. 3 and ground.
- Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) present?

YES: Go to Step 4.

NO: Check harness connector A-03 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector A-03 is in good condition, repair an open circuit between fusible link (5) and MFI relay connector B-22X (terminal No. 2, No. 3). Then confirm that the malfunction symptom is eliminated.




STEP 4. Check harness connector D-133 at PCM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 5.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.

STEP 5. Measure the ignition switch-IG signal voltage at PCM harness side connector D-133.




1. Disconnect the connector D-133 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.




3. Measure the voltage between terminal No. 50 and ground.
- Voltage should be battery positive voltage.

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

Q: Is battery positive voltage (approximately 12 volts) present?

YES: Go to Step 6.

NO: Check harness connector E-111, D-02, D-28 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector E-111, D-02, D-28 are in good condition, repair it because of open circuit between ignition switch connector D-204 (terminal No. 2) and PCM connector D-133 (terminal No. 50). Then confirm that the malfunction symptom is eliminated.

STEP 6. Measure the backup power supply voltage at PCM harness side connector D-133.




1. Disconnect the connector D-133 and measure at the harness side.




2. Measure the voltage between terminal No.58 and ground.
- Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) present?

YES: Go to Step 7.

NO: Check harness connector A-03 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector A-03 is in good condition, repair an open circuit between fusible link (5) and PCM connector D-133 (terminal No. 58). Then confirm that the malfunction symptom is eliminated.

STEP 7. Check the continuity at PCM harness side connector D-133.




1. Disconnect the connector D-133 and measure at the harness side.




2. Check for the continuity between terminal No. 33, No. 42 and ground.
- Should be less than 2 Ohms.

Q: Is the continuity normal?

YES: Go to Step 8.

NO: Check harness connector D-14 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector D-14 is in good condition, repair an open circuit or harness damage between PCM connector D-133 (terminal No. 33, No. 42) and ground. Then confirm that the malfunction symptom is eliminated.

STEP 8. Measure the power supply voltage at PCM harness side connector D-133.




1. Disconnect the connector D-133 and measure at the harness side.




2. Measure the voltage between terminal No.57 and ground.
- Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) present?

YES: Go to Step 9.

NO: Repair an open circuit between MFI relay connector B-22X (terminal No. 4) and PCM connector D-133 (terminal No. 57). Then confirm that the malfunction symptom is eliminated.

STEP 9. Measure the power supply voltage at PCM harness side connector D-133.




1. Disconnect the connector D-133 and measure at the harness side.
2. Using a jumper wire, connect terminal No. 57 to ground.




3. Measure the voltage between terminal No. 34, No. 43 and ground.
- Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) present?

YES: Replace the PCM. Then confirm that the malfunction symptom is eliminated.

NO: Check harness connector D-116 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector D-116 is in good condition, repair an open circuit between MFI relay connector B-22X (terminal No. 1) and PCM connector D-133 (terminal No. 34, No. 43). Then confirm that the malfunction symptom is eliminated.
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