DIAGNOSIS Required Special Tools: • MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: V.C.I. MB991827: USB Cable MB991911: Main Harness B • MB991348: Test Harness Set

STEP 1. Using scan tool MB991958, check actuator test item 01, 02, 03, 04: Injectors.

To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. (1) Connect scan tool MB991958 to the data link connector. (2) Start the engine and run at idle. (3) Set scan tool MB991958 to the actuator testing mode for item 01, 02, 03, 04 Injectors. (4) Warm up the engine to normal operating temperature: 80°C to 95°C (176°F to 203°F). • Does the idle state worsen when the injector is cut off. (Does idling become unstable or does the engine stall.) (5) Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the actuator operating properly? YES: 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 . NO: Go to Step 2.

STEP 2. Check the connector at injector for damage.

a.Check connector B-22 at No. 1 cylinder. b.Check connector B-20 at No. 2 cylinder. c.Check connector B-18 at No. 3 cylinder. d.Check connector B-17 at No. 4 cylinder. Q: Is the connector in good condition? YES: Go to Step 3. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 10.

STEP 3. Check the injector.

(1) Disconnect the injector connector B-22 <No. 1 cylinder> or B-20 <No. 2 cylinder> or B-18 <No.3 cylinder> or B-17 <No.4 cylinder>.

(2) Measure the resistance between injector side connector terminal No. 1 and No. 2. Standard value: 10.5 - 13.5 ohms [at 20°C (68°F)] Q: Is the resistance between 10.5 and 13.5 ohms [at 20°C (68°F)]? YES: Go to Step 4. NO: Replace the injector. Then go to Step 10.

STEP 4. Measure the power supply voltage at injector connector.

(1) Disconnect connector B-22 <No. 1 cylinder> or B-20 <No. 2 cylinder> or B-18 <No. 3 cylinder> or B-17 <No. 4 cylinder> and measure at the harness side. (2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between terminal No. 1 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: Go to Step 5.

STEP 5. Check connector B-12X at MFI relay for damage.

Q: Is the connector in good condition? YES: Repair harness wire between MFI relay connector and injector connector because of open circuit or short circuit to ground. a.Repair harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-22 (terminal No. 1) at No. 1 cylinder. b.Repair harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-20 (terminal No. 1) at No. 2 cylinder. c.Repair harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-18 (terminal No. 1) at No. 3 cylinder. d.Repair harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-17 (terminal No. 1) at No. 4 cylinder. • Then go to Step 10. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 10.

STEP 6. Check for harness damage between MFI relay connector and injector connector.

a.Check the harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-22 (terminal No. 1) at No.1 cylinder. b.Check the harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-20 (terminal No. 1) at No.2 cylinder. c.Check the harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-18 (terminal No. 1) at No.3 cylinder. d.Check the harness wire between MFI relay connector B-12X (terminal No. 4) and injector connector B-17 (terminal No. 1) at No.4 cylinder. Q: Is the harness wire in good condition? YES: Go to Step 7. NO: Repair it. Then go to Step 10.

STEP 7. Check harness connector C-121 at ECM <M/T> or harness connector C-120 at PCM <A/T> for damage.

Q: Is the harness connector in good condition? YES: Go to Step 8. NO: Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 10.

STEP 8. Check for open circuit and short circuit to ground and harness damage between injector connector and ECM connector <M/T> or PCM connector <A/T>.

a.Check the harness wire between injector connector B-22 (terminal No. 2) and ECM connector C-121 (terminal No. 1) <M/T> or PCM connector C-120 (terminal No. 1) <A/T> at No.1 cylinder. b.Check the harness wire between injector connector B-20 (terminal No. 2) and ECM connector C-121 (terminal No. 14) <M/T> or PCM connector C-120 (terminal No. 9) <A/T> at No.2 cylinder. c.Check the harness wire between injector connector B-18 (terminal No. 2) and ECM connector C-121 (terminal No. 2) <M/T> or PCM connector C-120 (terminal No. 24) <A/T> at No.3 cylinder. d.Check the harness wire between injector connector B-17 (terminal No. 2) and ECM connector C-121 (terminal No. 15) <M/T> or PCM connector C-120 (terminal No. 2) <A/T> at No.4 cylinder. Q: Is the harness wire in good condition? YES: Go to Step 9. NO: Repair it. Then go to Step 10.

STEP 9. Using the oscilloscope, check the injector.

(1) Disconnect the injector connector B-22 <No. 1 cylinder> or B-20 <No. 2 cylinder> or B-18 <No. 3 cylinder> or B-17 <No. 4 cylinder> and connect the test harness special tool (MB991348) in between. (All terminals should be connected.)

(2) Connect the oscilloscope probe to the injector side connector terminal No. 2. NOTE: When measuring with the ECM or PCM side connector, connect an oscilloscope probe to the each of the following terminals. • ECM terminal No. 1 or PCM terminal No. 1 at No. 1 cylinder. • ECM terminal No. 14 or PCM terminal No. 9 at No. 2 cylinder. • ECM terminal No. 2 or PCM terminal No. 24 at No. 3 cylinder. • ECM terminal No. 15 or PCM terminal No. 2 at No. 4 cylinder. (3) Start the engine and run at idle.

(4) Measure the waveform. • The waveform should show a normal pattern similar to the illustration. (5) Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the waveform normal? YES: 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 . NO: Replace the ECM or PCM. Then go to Step 10.