EVAP System Monitor Component Checks
Additional malfunctions that are identified as part of the evaporative system integrity check are as follows:
The Canister Purge Valve (CPV) output circuit is checked for opens and shorts (P0443)
Note that a stuck closed CPV generates a P0455, a leaking or stuck open CPV generates a P1450.
| DTCs | P0443 - Evaporative Emission System Purge Control Valve "A" Circuit |
| Monitor execution | continuous |
| Monitor Sequence | None |
| Sensors OK | not applicable |
| Monitoring Duration | 5 seconds to obtain smart driver status |
| P0443 (CPV): open/shorted at 0 or 100% duty cycle |
The Canister Vent Solenoid output circuit is checked for opens and shorts (P0446), a stuck closed CVS generates a P1450, a leaking or stuck open CVS generates a P0455.
| DTCs | P0446 - Canister Vent Solenoid Circuit |
| Monitor execution | continuous |
| Monitor Sequence | None |
| Sensors OK | not applicable |
| Monitoring Duration | 5 seconds to obtain smart driver status |
| P0446 (Canister Vent Solenoid Circuit): open/shorted |
The Evap Switching Valve (EVAPSV) output circuit is checked for opens and shorts (P2418).
| DTCs | P2418 - Evap Switching Valve Circuit |
| Monitor execution | continuous |
| Monitor Sequence | None |
| Sensors OK | not applicable |
| Monitoring Duration | 5 seconds to obtain smart driver status |
| P2418 (Evap Switching Valve Circuit): open/shorted |
The Fuel Tank Pressure Sensor input circuit is checked for out of range values (P0452 short, P0453 open), noisy readings (P0454 noisy) and an offset (P0451 offset).
Note that an open power input circuit or stuck check valve generates a P1450.
| FTP volts = [ Vref * (0.14167 * Tank Pressure) + 2.6250 ] / 5.00 | ||
| Volts | A/D Counts in PCM | Fuel Tank Pressure, Inches H 2 O |
| 0.100 | 20 | -17.82 |
| 0.500 | 102 | -15.0 |
| 1.208 | 247 | -10.0 |
| 2.625 | 464 | 0 |
| 3.475. | 712 | 6.0 |
| 4.750 | 973 | 15.0 |
| 4.90 | 1004 | 16.06 |
| DTCs | P0452 - Fuel Tank Pressure Sensor Circuit Low P0453 - Fuel Tank Pressure Sensor Circuit High P0454 - Fuel Tank Pressure Sensor Intermittent/Erratic (noisy) |
| Monitor execution | continuous |
| Monitor Sequence | None |
| Sensors OK | not applicable |
| Monitoring Duration | 5 seconds for electrical malfunctions, 10 seconds for noisy sensor test |
| P0452 (Fuel Tank Pressure Sensor Circuit Low): < -17.82 in H2
O P0453 (Fuel Tank Pressure Sensor Circuit High): > 16.06 in H2 O P0454 (Fuel Tank Pressure Sensor Circuit Noisy): > open circuit, short circuit or > 4 in H2 O change between samples, sampled every 100 msec |
| DTCs | P0451 - Fuel Tank Pressure Sensor Range/Performance (offset) |
| Monitor execution | once per driving cycle |
| Monitor Sequence | No P0443 or P1450 DTCs |
| Sensors OK | not applicable |
| Monitoring Duration | < 1 second |
| Entry Condition | Minimum | Maximum |
| Ignition key on, engine off, engine rpm | 0 rpm | |
| Purge Duty Cycle | 0% | |
| Engine off (soak) time | 4 - 6 hours | |
| Fuel Tank Pressure Sensor Variation during test | 0.5 in H2 O | |
| Battery Voltage | 11.0 volts |
| Fuel tank pressure at key on, engine off is 0.0 in H2 O +/- 2.0 in H2 O |
The Fuel Level Input is checked for out of range values (opens/ shorts). The FLI input is obtained from the serial data link from the instrument cluster. If the FLI signal is open or shorted, the appropriate DTC is set (P0462 circuit low and P0463 circuit high).
Vehicles with a "saddle tank" (a tank that wraps over the axle) have two fuel level senders. The FLI input is obtained from the serial data link from the instrument cluster. If the FLI signal is open or shorted, the appropriate DTC is set (P2067 circuit low and P2068 circuit high). A "jet pump" pumps fuel from the passive side of the saddle tank to the active side of the saddle tank where the main fuel pump supplies the engine with fuel. This means that the active side of the fuel tank typically has a high fuel level reading because it constantly filled by the jet pump. For purposes of computing vehicle fuel level, the two FLI readings are averaged together into one signal that represents the combined fuel level.
Finally, the Fuel Level Input is checked for noisy readings. If the FLI input continues to change > 40% between samples, a P0461 DTC is set.
| DTCs | P0461 - Fuel Level Sensor A Circuit Noisy P0462 - Fuel Level Sensor A Circuit Low P0463 - Fuel Level Sensor A Circuit High P2067 - Fuel Level Sensor B Circuit Low P2068 - Fuel Level Sensor B Circuit High |
| Monitor execution | continuous |
| Monitor Sequence | None |
| Sensors OK | not applicable |
| Monitoring Duration | 30 seconds for electrical malfunctions, |
| P0460 or P0462 (Fuel Level Input Circuit Low): < 5 ohms (< 1 A/D count) P0460 or P0463 (Fuel Level Input Circuit High): > 200 ohms (>253 A/D counts) P0461 (Fuel Level Input Noisy): > 40% change between samples, > 100 occurrences, sampled every 0.100 seconds |
The FLI signal is also checked to determine if it is stuck. "Fuel consumed" is continuously calculated based on PCM fuel pulse width summation as a percent of fuel tank capacity. (Fuel consumed and fuel gauge reading range are both stored in KAM and reset after a refueling event or DTC storage.) If the there is an insufficient corresponding change in fuel tank level, a P0460 DTC is set.
Different malfunction criteria are applied based on the range in which the fuel level sensor is stuck.
In the range between 15% and 85%, a 30% difference between fuel consumed and fuel used is typical. The actual value is based on the fuel economy of the vehicle and fuel tank capacity.
In the range below 15%, a 40% difference between fuel consumed and fuel used is typical. The actual value is based on reserve fuel in the fuel tank and the fuel economy of the vehicle.
In the range above 85%, a 60% difference between fuel consumed and fuel used is typical. The actual value is based on the overfill capacity of the fuel tank and the fuel economy of the vehicle. Note that some vehicles can be overfilled by over 6 gallons.
| DTCs | P0460 - Fuel Level Input Circuit Stuck |
| Monitor execution | continuous |
| Monitor Sequence | None |
| Sensors OK | not applicable |
| Monitoring Duration | Between 15 and 85%, monitoring can take from 100 to 120 miles to complete |
| P0460 (Fuel Level Input Stuck): Fuel level stuck at greater than 90%: > 60% difference in calculated fuel tank capacity consumed versus change in fuel level input reading Fuel level stuck at less than 10%: > 30% difference in calculated fuel tank capacity consumed versus change in fuel level input reading Fuel level stuck between 10% and 90%: > 25% difference in calculated fuel tank capacity consumed versus change in fuel level input reading |
The Evap Monitor Microprocessor is checked for proper microprocessor operation or loss of CAN communication with the main microprocessor (P260F). Applies only if EONV is in separate microprocessor.
| DTCs | P260F - Evap System Monitoring Processor Performance |
| Monitor Execution | continuous |
| Monitor Sequence | None |
| Sensor OK | not applicable |
| Monitoring Duration | 5 seconds |
Evap Switching Valve (EVAPSV) Diagnostics
The Evap Switching Valve (EVAPSV) is included on HEV applications for 2009 Model Year. It is very similar to the Fuel Tank Isolation Valve (FTIV) used in previous model years. The Evap Switching Valve is also known as a Vapor Blocking Valve (VBV). The purpose of the EVAPSV is to isolate the fuel tank from the rest of the evaporative system so that the Canister Purge Valve (CPV) can purge more aggressively with minimal risk of purge vapor slugs being ingested into the intake.
The EVAPSV is normally closed during engine operation, but may vent during a drive to relieve positive pressure. The exact pressure points at which the valve opens and closes are vehicle dependent. When the vehicle is in a key-off state, the EVAPSV is not powered and the valve is open.
The VBV circuit and functional diagnostics will set the following DTCs:
P2418 - EVAPSV circuit fault
P2450 - EVAPSV stuck open fault
The EVAPSV circuit diagnostics are very similar to that of the Canister Purge Valve (CPV) and Canister Vent Solenoid (CVS). See Evap System Monitor Component Checks below.
A diagram of an evaporative system with an EVAPSV (shown as a VBV) is shown below:
The Evaporative System monitor performs a functional check of the EVAPSV in Phase 3 of the evap monitor cruise tests if the 0.040" leak test passes. At the end of Phase 2, tank pressure will be in the range of -8 to -5 "H2 0 and the EVAPSV will be open. At the beginning of Phase 3, the EVAPSV is commanded closed and the CVS is commanded open. If the EVAPSV fails to close, there will be a rapid pressure loss in the fuel tank. If this pressure loss exceeds a calibrated threshold, a P2450 DTC is set. (Requires 2 or 3 failures in a row during a driving cycle (calibratable)). If the fault is present on a second driving cycle, the MIL will be illuminated.
| DTCs | P2450 |
| Monitor Execution | once per driving cycle |
| Monitor Sequence | Run after evap 0.040" cruise test |
| Sensors/Components OK | MAF, IAT, VSS, ECT, TP, FTP, CPV, CVS |
| Monitoring Duration | 30 seconds (see disablement condition below) |
| Entry Condition | Minimum | Maximum |
| 0.040" Cruise Test completes |
| Change in fuel fill level: > 15% |
| P2418: Presence of short, open, or intermittent fault for more than 5 seconds P2450: Pressure loss > 3" H2 0 during phase 3. |
| Test ID | Comp ID | Description | Units |
| $3D | $82 | Vapor blocking valve performance (P2450) | Pa |
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NOTE:
Default values (0.0 Pa) will be displayed for all the above TIDs if the evap monitor has never completed. Each TID is associated with a particular DTC. The TID for the appropriate DTC will be updated based on the current or last driving cycle, default values will be displayed for any phases that have not completed.
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Blocked Purge Line Diagnostics
If an in-line Fuel Tank Pressure Transducer is used, it is possible for a blockage to occur between the Fuel Tank Pressure Transducer (FTPT) and fuel tank. If this occurs, the evap monitor would run and pass all leak check diagnostics even if there is a leak at the fuel cap. (The blockage will make the system look sealed despite the leak.). The blocked line diagnostic looks for a rapid drop in pressure during Phase 0 of the cruise test. This rapid pressure drop occurs because the Canister Purge Valve (CPV) applies a vacuum to just the canister and evap lines. Upon seeing an excessively fast pressure drop in Phase 0, the evap monitor will invoke a special execution of Phase 3 & 4 where a CPV pressure pulse is applied to the evap system. This pressure pulse is at a very low flow and short duration (0.5 -1.0 seconds) to avoid driveability issues. If this intrusive test fails, the Phase 0 test and the intrusive test are repeated 2 or 3 times prior to setting a P144A DTC.
Diagram of an evaporative system with a blockage is shown below:
| DTC | P144A |
| Monitor execution | once per drive cycle |
| Monitor Sequence | Runs during Phase 0 of evap 0.040" cruise test. Performs an intrusive test in Phase 3 & 4 to confirm a fault. |
| Sensor/Components OK | MAF, IAT, VSS, ECT, CKP, TP, FTP, CPV, CVS |
| Monitoring Duration | 30 seconds (see disablement conditions below) |
| Entry condition | Minimum | Maximum |
| General 0.040" Cruise Test conditions apply | ||
| Air mass high enough for intrusive portion of test | 1.5 (lb/min) | |
| Manifold vacuum high enough for intrusive portion of test | 5 "Hg | |
| Not in open loop fueling | ||
| CPV purging |
| All items cited under entry conditions apply. |
| P144A: Phase 0 portion of test delta pressure < -5 "H2
0/sec P144A: Phase 3 & 4 (intrusive test) pressure response < -2 "H2 0 |
| Test ID | Comp ID | Description | Units |
| $3D | $80 | Blocked Evap System Line - Screening test (P144A) | Pa/sec |
| $3D | $81 | Blocked Evap System Line - Fault confirmation test (P144A) | Pa |
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NOTE:
Default values (0.0) will be displayed for all the above TIDs if the evap monitor has never completed. Each TID is associated with a particular DTC. The TID for the appropriate DTC will be updated based on the current or last driving cycle, default values will be displayed for any phases that have not completed.
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Single Path Purge Check Valve Diagnostics
Boosted applications use a mechanical check valve between the intake manifold and the Canister Purge Valve (CPV). The purpose of this check valve is to prevent reverse flow through the evaporative emissions system under boosted conditions. The check valve is a simple diaphragm type valve were the rubber diaphragm slides inside a cylinder and is pushed against a stop under boost closing off flow through the valve. While at atmosphere or under vacuum the valve is pulled off the stop allowing flow from the evaporative system to the intake manifold. The check valve diagnostic looks for a failed open, improperly installed, or missing valve that could result in intake manifold vapors being pushed back into the evaporative emissions system (see figure below). A failed check valve is detected if the rate of rise in Fuel Tank Pressure Sensor is greater than a calibratable threshold while the Canister Vent Valve is closed, Canister Purge Valve open, and the engine is boosted above a minimum level (under boost the system should be sealed if the check valve is operating properly). This condition will set DTC P144C.
Figure: System schematic showing the potential for reverse flow if the check valve is failed.
| DTC | P144C Evaporative Emission System Purge Check Valve Performance |
| Monitor execution | Once per drive cycle, during boosted operation |
| Monitor Sequence | None |
| Sensor/Component OK | ECT/CHT, IAT, MAP, CPV, FTPT, FLI, BARO, TIP |
| Monitoring Duration | 5 to 10 seconds depending on level of boost |
| Entry Condition | Minimum | Maximum |
| Ambient temperature | 40 °F | 95 °F |
| Battery Voltage | 11.0 Volts | |
| Fuel Level | 15% | 85% |
| Engine Coolant Temperature (CHT/ECT) | 160 °F | |
| Atmospheric Pressure (BARO) | 23" Hg | |
| Boost Pressure (MAP - BARO) | 4 to 8" Hg | |
| Engine Delta Load | 0.2 | |
| Vehicle Acceleration | 0.5 mph/sec |
| Pressure Rise Rate (delta pressure / delta time) > 0.50 " H2
O/sec Threshold is a function of fuel level with a range of 0.5 to 1.0 |
Dual Path Purge Check Valve Diagnostics
Boosted applications that have a lower power-to-weight ratio use two purge flow paths to allow purge under boost conditions in addition to normal vacuum conditions.
Dual path purge applications use a mechanical check valve 1 (CV1) between the intake manifold and the Canister Purge Valve (CPV). During non-boosted conditions, purge vapors go through check valve 1 before entering the intake. The purpose of this check valve is to prevent reverse flow through the evaporative emissions system under boosted conditions. The check valve is a simple diaphragm type valve were the rubber diaphragm slides inside a cylinder and is pushed against a stop under boost closing off flow through the valve.
A second identical check valve 2 (CV2) is used to facilitate purging during boost. During boosted conditions, a venturi device, called an ejector, is used to generate the needed vacuum for purging. The purge vapors flow through CV2, the turbo charger, and the charge air cooler before entering the intake manifold.
The check valve diagnostic looks for a failed open CV1, a failed closed CV2, a failed ejector, an improperly installed CV1 or CV2, or missing CV1 that could result in intake manifold vapors being pushed back into the evaporative emissions system or lack of purge under boost.
A failed CV1 is detected if the rate of rise in Fuel Tank Pressure Sensor is greater than a calibratable threshold while the Canister Vent Valve is closed, Canister Purge Valve open, and the engine is boosted above a minimum level. Under boost, the system should be sealed if the check valve is operating properly. This condition will set DTC P144C.
A failed CV2 is detected if the rate of change of ejector generated vacuum is relatively flat within a threshold window during boosted conditions. This will set DTC P144C. Steep vacuum slopes for CV2 are indicative of good functioning valves. See the figure below for CV1/CV2 pass and fail ranges.
| DTC | P144C - Evaporative Emission System Purge Check Valve Performance |
| Monitor execution | Once per driving cycle, during boosted operation |
| Monitor Sequence | None |
| Sensors/Components OK | ECT/CHT, IAT, MAP, CPV, CVV, FTPT, FLI, BARO, TIP, WASTEGATE |
| Monitoring Duration | 5 to 10 seconds depending on level of boost |
| Entry Condition | Minimum | Maximum |
| Ambient air temperature | 40 °F | 105 °F |
| Battery Voltage | 11.0 Volts | |
| Fuel level | 15% | 90% |
| Engine Coolant Temperature | 160 °F | |
| Atmospheric Pressure (BARO) | 23" Hg | |
| Boost Pressure (MAP - BARO) | 8" Hg |
| CV1- Pressure Rise Rate (delta pressure / delta time) > 1 " H2
O/sec CV1- Threshold is a function of fuel level with a range of 1.5 to 2.6 CV2- Vacuum Rate (delta vacuum / delta time) >-0.4 and < 0.5 H2 O/sec CV2- Threshold is a function of fuel level with a range of 0.5 to 0.7 for the upper band and -0.4 to -0.3 for the lower band |