The evaporative emission control system prevents hydrocarbon vapors from escaping from the fuel tank into the atmosphere where they could form photochemical smog. Gasoline vapors are collected in the charcoal canister. The Fuel Tank Pressure Sensor (FTPS) is an integral part of the evaporative monitoring system. The PCM monitors the FTPS signal to detect vacuum decay and excess vacuum. The FTPS measures the difference between the air pressure inside the fuel tank and outside air pressure to check the purge control solenoid valve operation and for leak detection in the evaporative emission control system by monitoring pressure and vacuum levels in the fuel tank during the purge control solenoid valve operating cycles.
The PCM monitors pressure in the fuel tank by means of Fuel Tank Pressure Sensor (FTPS) during purge control valve opening or closing phase. This monitoring will determine if pressure sensor signal is stuck. The PCM sets DTC P0451 if pressure variation is smaller than the predetermined threshold.
Item | Detecting Condition | Possible Cause | |
Case 1 | DTC Strategy |
•
Signal Stuck in range | 1. Poor connection or damaged harness 2. Faulty FTPS 3. Faulty PCSV 4. Fuel Cap missing |
Enable Conditions |
•
Vehicle Speed>31mph at least one time during driving cycle
•
Canister Purge Flow > 3.3 lb/h (Uninterupted 15 sec.)
•
Fuel level < 85%
•
Modeled Ambient Temperature > -10℃ (14℉)
•
Canister Load < 0.5
•
No MIL illuminated for DTCs | ||
Threshold Value |
•
Signal Variation < 40 mV | ||
Diagnostic Time |
•
15 Seconds | ||
Case 2 | DTC Strategy |
•
Signal Stuck High | |
Enable Conditions |
•
Canister Purge Flow > 3.3 lb/h (Uninterupted 15 sec.)
•
Fuel level < 85%
•
Modeled Ambient Temperature > -10℃ (14℉)
•
Canister Load < 0.5
•
Coolant Temp. > 50℃ (122℉)
•
No MIL illuminated for DTCs | ||
Threshold Value |
•
Fuel Tank Pressure > 400 Pa | ||
Diagnostic Time |
•
30 Seconds | ||
Case 3 | DTC Strategy |
•
Signal Stuck Low | |
Enable Conditions |
•
Canister Purge Valve closed
•
Fuel level < 85%
•
Modeled Ambient Temperature > -10℃ (14℉)
•
Coolant Temp. > -10℃ (14℉)
•
No MIL illuminated for DTCs | ||
Threshold Value |
•
-3500 Pa < Fuel Tank Pressure < -1100 Pa | ||
Diagnostic Time |
•
40 Seconds | ||
Mil On Condition |
•
2 Drive Cycles | ||
PesrPesr | -3.75 kPa(-1.10 inHg) | 0 kPa(0 inHg) | 1.25 kPa(0.37 inHg) |
FTPS output voltage | 4.5 V | 1.5 V | 0.5 V |
