DTC P0451: Fuel Tank Pressure Sensor Circuit Range/Performance Problem
- Remove fuel filler cap. Turn ignition switch on. Monitor Fuel Tank Pressure (FTP) sensor voltage with scan tool or measure voltage (backprobe) between PCM 31-pin "C" harness connector terminal No. 18 (Green/Yellow wire) and PCM 32-pin "A" harness connector terminal No. 29 (Light Green wire - A/T) or PCM 31-pin "A" harness connector terminal No. 28 (Green/Yellow wire) and PCM 31-pin "E" harness connector terminal No. 28 (Light Green wire - M/T). See Figure or Figure . See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. If about 2.5 volts are present, go to next step. If about 2.5 volts are not present, replace FTP sensor.
- Turn ignition switch off. Open fuel vent assembly cover in front of EVAP canister. See Fig 1
. Disconnect vacuum hose between EVAP 2-way valve and FTP sensor at EVAP 2-way valve. Connect vacuum pump to open end of disconnected hose.CAUTION: Damage to fuel tank pressure sensor may occur if vacuum is applied after voltage drops to 1.5 volts.
- Turn ignition switch on. Measure voltage between PCM 31-pin "C" harness connector terminal No. 18 (Green/Yellow wire) and PCM 32-pin "A" harness connector terminal No. 29 (Light Green wire - A/T) or PCM 31-pin "A" harness connector terminal No. 28 (Green/Yellow wire) and PCM 31-pin "E" harness connector terminal No. 28 (Light Green wire - M/T). Carefully pump vacuum one stroke at a time. Voltage should drop smoothly from about 2.5 volts down to about 1.5 volts. If voltage drops to about 1.5 volts and holds, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM. If voltage does not drop to about 1.5 volts and hold, replace FTP sensor.