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DTC P0271: Injector Circuit High Input - Cylinder 4

 
 
 
 
CIRCUIT OPERATION
  • The injector power is supplied from the MFI relay.
  • The ECM controls the injector by turning the power transistor in the ECM "ON" and "OFF".
 
 
TECHNICAL DESCRIPTION
  • The amount of fuel injected by the injector is controlled by the amount of continuity time the coil is grounded by the ECM.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • The ECM detects short malfunction.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Condition
  • Engine is running.
  • Battery positive voltage is between 10 and 16.5 volts.
Judgment Criterion
  • The coil current is more than 4.5 amperes with the injector driving for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • None
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 23 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • No. 4 cylinder injector failed.
  • Shorted No. 4 cylinder injector circuit, harness damage or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tools:
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: V.C.I.
    • MB991827: USB Cable
    • MB991910: Main Harness A
  • MB991658: Test Harness
  • MB992110: Power Plant ECU Check Harness
STEP 1. Using scan tool MB991958, check actuator test item 1: Injectors.
cautionTo 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) Warm up the engine to normal operating temperature: 80°C to 95°C (176°F to 203°F).
(4) Set scan tool MB991958 to the actuator testing mode for item 1 Injectors.
  • The idle should become slightly rougher.
(5) Turn the ignition switch to the "LOCK" (OFF) position.
Is the actuator 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 .
Go to Step 2.
 
STEP 2. Check harness connector B-106 at No. 4 cylinder injector for damage.
Is the harness connector in good condition?
Go to Step 3.
Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 7.
 
STEP 3. Check the No. 4 cylinder injector.
(1) Disconnect the No. 4 cylinder injector connector B-106.
(2) Measure the resistance between injector side connector terminal No. 1 and No. 2.
Standard value: 10.5 - 13.5 Ω [at 20°C (68°F)]
Is the measured resistance between 10.5 and 13.5 Ω [at 20°C (68°F)]?
Go to Step 4.
Replace the No. 4 cylinder injector. Then go to Step 7.
 
STEP 4. Check harness connector B-26 at ECM for damage.
Is the harness connector in good condition?
Go to Step 5.
Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 7.
 
STEP 5. Check for short circuit to power supply and harness damage between No. 4 cylinder injector connector B-106 (terminal No. 2) and ECM connector B-26 (terminal No. 19).
Is the harness wire in good condition?
Go to Step 6.
Repair it. Then go to Step 7.
 
STEP 6. Using the oscilloscope, check the No. 4 cylinder injector.
(1) Disconnect the No. 4 cylinder injector connector B-106 and connect the test harness special tool MB991658 between the separated connectors. (All terminals should be connected.)
(2) Connect the oscilloscope probe to the injector side connector terminal No. 2.
noteWhen checking with the ECM side connector, disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors. Then connect the oscilloscope probe to the check harness connector terminal No. 2.
(3) Start the engine and run at idle.
(4) Check the wave pattern.
  • The wave pattern should show a normal pattern similar to the illustration.
(5) Turn the ignition switch to the "LOCK" (OFF) position.
Is the wave pattern normal?
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 go to Step 7.
 
STEP 7. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 23 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0271 set?
Retry the troubleshooting.
The inspection is complete.