Part 1
DTC P0451: Evaporative Emission Control System Pressure Sensor Range/PerformanceSystem Diagram:
Fuel Tank Differential Pressure Sensor Circuit Part 1:
Fuel Tank Differential Pressure Sensor Circuit Part 2:
CIRCUIT OPERATION
- The ECM (terminals81)
- The fuel tank differential pressure sensor (terminal 1) returns a voltage signal to the ECM (terminal81)
TECHNICAL DESCRIPTION
- The ECM
- The ECM
DTC SET CONDITIONS
Check Conditions:
- Throttle valve is closed.
- Vehicle speed is 1.5 km/h (0.93 mph) or less.
Judgment Criteria
- If the voltage signal from the fuel tank differential pressure sensor changes by 0.2 volt or more, DTC P0451 will set. The code may also set if a sudden pressure fluctuation occurs twenty times while the engine is idling, and then eight consecutive times during normal driving.
NOTE: If the number of sudden pressure fluctuations does not reach twenty during any one period of engine idling, or if the ignition switch is turned OFF, the counter will reset to zero.
NOTE: The conditions for deviating from idling operation are as follows:
- Engine speed is greater than 2,500 r/min.
- Vehicle speed is 15 km/h (9.3 mph) or greater.
- Volumetric efficiency is 55 percent or greater.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Malfunction of the fuel tank differential pressure sensor.
- A damaged harness in the fuel tank differential pressure sensor circuit.
- Malfunction of the ECM
OVERVIEW OF TROUBLESHOOTING
- DTC P0451 can be set by a faulty fuel differential pressure sensor or related circuit, or ECM
- To check a system blockage, do a performance test which uses a mechanical vacuum gauge and scan tool MB991502 set on the fuel tank differential pressure sensor (TANK PRS SNSR 73.) The mechanical gauge reading is used to verify scan tool MB991502 reading. A comparison of the mechanical gauge to scan tool MB991502 determines the problem in the system.
DIAGNOSIS
Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991658: Test Harness Set
STEP 1. Using scan tool MB991502, check data list item 73: Fuel Tank Differential Pressure Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Disconnect hose G from the evaporative emission canister side, and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Set scan tool MB991502 to the data reading mode for item 73, Fuel Tank Differential Pressure Sensor.
- The fuel tank pressure reading on the scan tool should be -1.5 to +1.5 kPa (-0.443 to +0.443 inHg).
6. Connect an evaporative emission system pressure pump (Miller number 6872A) to the fuel filler neck and pressurize the fuel tank.
- The fuel tank pressure reading should increase.
7. Turn the ignition switch to the "LOCK" (OFF) position. Disconnect scan tool MB991502.
8. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
9. Connect hose G to the canister.
Q: Is the fuel tank pressure between -1.5 and +1.5 kPa (-0.443 and +0.443 inHg)?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/ Inspection Service Points - Intermittent Malfunction. Go to Step 29.
NO: Go to Step 2.
STEP 2. Measure the signal voltage at intermediate connector D-14 by backprobing.
1. Remove the rear seat cushion. (Refer to Rear Seat)
2. Pull up the carpet.
3. Disconnect hose G from the evaporative emission canister side, and plug the hose.
4. Turn the ignition switch to the "ON" position.
5. Remove the fuel cap.
6. Measure the voltage between connector D-14 terminal 11 and ground by backprobing.
- The measured voltage should be between 2.0 and 3.0 volts.
7. Connect an evaporative emission system pressure pump (Miller number 6872A) to the fuel filler neck and pressurize the fuel tank.
- The fuel tank pressure reading should increase.
8. Turn the ignition switch to the "LOCK" (OFF) position.
9. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
10. Connect hose G to the canister.
Q: Is the measured voltage between 2.0 and 3.0 volts?
YES: Go to Step 3.
NO: Go to Step 8.
STEP 3. Measure the signal voltage at ECM connector C-117
1. Do not disconnect ECM connector C-117
2. Disconnect hose G from the evaporative emission canister side, and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Measure the voltage between connector C-117 terminal 61
- The measured voltage should be between 2.0 and 3.0 volts.
6. Connect an evaporative emission system pressure pump (Miller number 6872A) to the fuel filler neck and pressurize the fuel tank.
- The fuel tank pressure reading should increase.
7. Turn the ignition switch to the "LOCK" (OFF) position.
8. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
9. Connect hose G to the canister.
Q: Is the measured voltage between 2.0 and 3.0 volts?
YES: Go to Step 4.
NO: Go to Step 6.
STEP 4. Check intermediate connector D-14 and ECM
Q: Are the connectors and terminals in good condition?
YES: Go to Step 5.
NO: Repair or replace the damaged components. Refer to Harness Connector Inspection. Go to Step 29.
STEP 5. Using scan tool MB991502, check data list item 73: Fuel Tank Differential Pressure Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Disconnect hose G from the evaporative emission canister side, and plug the hose.
3. Turn the ignition switch to the "ON" position.
4. Remove the fuel cap.
5. Set scan tool MB991502 to the data reading mode for item 73, Fuel Tank Differential Pressure Sensor.
- The fuel tank pressure reading on the scan tool should be -1.5 to +1.5 kPa (-0.443 to +0.443 inHg).
6. Connect an evaporative emission system pressure pump (Miller number 6872A) to the fuel filler neck and apply pressure.
- The scan tool reading should increase.
7. Turn the ignition switch to the "LOCK" (OFF) position.
8. Disconnect the evaporative emission system pressure pump, and reinstall the fuel cap.
9. Connect hose G to the canister.
Q: Is the fuel tank pressure between -1.5 and +1.5 kPa (-0.443 and +0.443 inHg)?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/ Inspection Service Points - How to Cope with Intermittent Malfunction. Go to Step 29.
NO: Replace the ECM
STEP 6. Check intermediate connectors D-14, C-127, and C-124 and ECM
Q: Are the connectors and terminals in good condition?
YES: Go to Step 7.
NO: Repair or replace the faulty component. Refer to Harness Connector inspection.Go to Step 29.
STEP 7. Check the harness wire between ECM connector C-117 terminal 61
Q: Is the harness wire in good condition?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/ Inspection Service Points - How to Cope with Intermittent Malfunction. Go to Step 29.
NO: Repair the damaged harness wire. Go to Step 29.
STEP 8. Measure the 5-volt reference signal at intermediate connector D-14 by backprobing.
1. Do not disconnect intermediate connector D-14.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between connector D-14 terminal 9 and ground.
- The voltage should be between 4.8 and 5.2 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.8 and 5.2 volts?
YES: Go to Step 14.
NO: Go to Step 9.
STEP 9. Measure the 5-volt reference signal at ECM connector C-115
1. Do not disconnect ECM connector C-115
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between connector C-115 terminal 81
- The measured voltage should be between 4.8 and 5.2 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 4.8 and 5.2 volts?
YES: Go to Step 10.
NO: Go to Step 12.
STEP 10. Check intermediate connectors C-105, C-124, C-127, and D-14 and ECM connector C-115
Q: Are the connectors and terminals in good condition?
YES: Go to Step 11.
NO: Repair or replace the damaged components. Refer to Harness Connector inspection.Go to Step 29.
STEP 11. Check the harness wire between ECM connector C-115 terminal 81
Q: Is the harness wire in good condition?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/ Inspection Service Points - How to Cope with Intermittent Malfunction. Go to Step 29.
NO : Repair the damaged harness wire. Go to Step 29.