DTC P0451: FTP Sensor Range/Performance Problem Honda Civic VII

Special Tools Required

1. Vacuum Pump/Gauge, 0 - 30 in.Hg A973X-041-XXXXX

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1. Remove the fuel fill cap.
2. Turn the ignition switch ON (II).
3. Monitor fuel tank pressure (FTP) sensor voltage with the HDS, or measure voltage between ECM/PCM connector terminals E4 and E14. Is there about 2.5 V? YES - Go to step 4. NO - Replace the FTP sensor.
4. Turn the ignition switch OFF.
5. Disconnect the hose between the EVAP two way valve and the FTP sensor at the EVAP two way valve end.
6. Connect a vacuum pump to the open end of the hose.
7. Turn the ignition switch ON (II).
8. Monitor FTP sensor voltage with the HDS, or measure voltage between ECM/PCM connector terminals E4 and E14, and carefully squeeze the vacuum pump a little.
9. The voltage should smoothly drop from about 2.5 V down to about 1.5 V. Stop applying vacuum when the voltage drops to about 1.5 V or damage to the FTP sensor may occur. Does the voltage drop to about 1.5 V and hold? YES - Check for misrouted, leaking, or broken FTP sensor vacuum lines. If the vacuum lines are OK, update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck (see «ECM/PCM UPDATING, SUBSTITUTION AND REPLACEMENT»(ref-173106-S42338946762005031000000) ). If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM. NO - Replace the FTP sensor.

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1. Check the vacuum lines at the FTP sensor for misrouting, leakage, breakage, and clogging. Are the vacuum lines OK? YES - Go to step 2. NO - Repair or replace vacuum lines as necessary.
2. Reset the ECM/PCM (see «HOW TO RESET THE ECM/PCM»(ref-173106-S10389340332005031000000) ).
3. Remove the fuel fill cap.
4. Turn the ignition switch ON (II).
5. Monitor FTP sensor voltage with the HDS, or measure voltage between body ground and ECM/PCM connector terminal E14. Is there about 2.5 V? YES - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the FTP sensor and at the ECM/PCM. NO - Go to step 6.
6. Turn the ignition switch OFF.
7. Reinstall the fuel fill cap.
8. Disconnect the FTP sensor 3P connector.
9. Turn the ignition switch ON (II).
10. Measure voltage between FTP sensor 3P connector terminals No. 1 and No. 2. Is there about 5 V? YES - Go to step 11. NO - Repair open in the wire between the FTP sensor and the ECM/PCM (E5).
11. Measure voltage between FTP sensor 3P connector terminals No. 2 and No. 3. Is there about 5 V? YES - Replace the FTP sensor. NO - Go to step 12.
12. Turn the ignition switch OFF.
13. Disconnect ECM/PCM connector E (31P).
14. Check for continuity between FTP 3P connector terminal No. 3 and body ground. Is there continuity? YES - Repair short in the wire between the FTP sensor and the ECM/PCM (E14). NO - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck (see «ECM/PCM UPDATING, SUBSTITUTION AND REPLACEMENT»(ref-173106-S42338946762005031000000) ). If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.

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1. Check the vacuum lines at the FTP sensor for misrouting, leakage, breakage, and clogging. Are the vacuum lines OK? YES - Go to step 2. NO - Repair or replace vacuum lines as necessary.
2. Reset the ECM/PCM (see «HOW TO RESET THE ECM/PCM»(ref-173106-S10389340332005031000000) ).
3. Remove the fuel fill cap.
4. Turn the ignition switch ON (II).
5. Monitor FTP sensor voltage with the HDS, or measure voltage between body ground and ECM/PCM connector terminal E14. Is there about 2.5 V? YES - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the FTP sensor and at the ECM/PCM. NO - Go to step 6.
6. Turn the ignition switch OFF.
7. Reinstall the fuel fill cap.
8. Disconnect the FTP sensor 3P connector.
9. Turn the ignition switch ON (II).
10. Measure voltage between FTP 3P connector terminals No. 1 and No. 2. Is there about 5 V? YES - Go to step 15 . NO - Go to step 11.
11. Turn the ignition switch OFF.
12. Disconnect ECM/PCM connector E (31P).
13. Connect FTP sensor 3P connector terminal No. 2 to body ground with a jumper wire.
14. Check for continuity between ECM/PCM connector terminal E4 and body ground. Is there continuity? YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck (see «ECM/PCM UPDATING, SUBSTITUTION AND REPLACEMENT»(ref-173106-S42338946762005031000000) ). If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM. NO - Repair open in the wire between the FTP sensor and the ECM/PCM (E4).
15. Measure voltage between FTP sensor 3P connector terminals No. 2 and No. 3. Is there about 5 V? YES - Replace the FTP sensor. NO - Go to step 12.
16. Measure voltage between ECM/PCM connector terminals E4 and E14. Is there about 5 V? YES - Repair open in the wire between the FTP sensor and the ECM/PCM (E14). NO - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck (see «ECM/PCM UPDATING, SUBSTITUTION AND REPLACEMENT»(ref-173106-S42338946762005031000000) ). If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.