P1457 – Unable To Pull Vacuum In Tank / EVAP System – Leak Detected (Ford, Honda)

By Reinier (Contact Me)
Last Updated 2018-04-05
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P1457

Table of Contents

1. What Does Code P1457 Mean?
2. What are the common causes of code P1457?
3. What are the symptoms of code P1457?
4. How do you troubleshoot code P1457?
5. Codes Related to P1457
6. Get Help with P1457

What Does Code P1457 Mean?

OBD II fault code P1457 is most commonly defined as “Unable to Pull Vacuum in Tank”, and is set when the PCM (Powertrain Control Module) detects a fault that prevents the EVAP system from either pulling or maintaining a vacuum in the fuel tank. Note that although the definition, “Unable to Pull Vacuum in Tank” mainly applies to applications that use a vacuum to test the EVAP system for leaks, some manufacturers, most notably Honda/Acura, have assigned the definition “EVAP System- Leak Detected” to this code.

Typical EVAP systems consist of the fuel tank, fuel filler cap, electrical wiring and connectors, fuel lines, vacuum lines, various control solenoids and valves; a charcoal canister, flow/pressure sensors, and in some cases a dedicated air pump to pressurize the EVAP system for leak detection purposes.

The purpose of the EVAP system is to capture fuel vapors before they can escape into the atmosphere. This is accomplished by temporarily storing fuel vapors in a charcoal-filled canister, before routing the collected vapors to the engine via vacuum lines to the engine to be combusted as part of the air/fuel mixture.

In terms of operation, vacuum-tested EVAP systems are sealed by the PCM by closing the vent valve during a self-test cycle. Assuming that all other components are fully functional, the engine vacuum creates a small vacuum in the EVAP system that causes a negative pressure, which negative pressure is converted into a varying signal voltage by the Fuel Tank Pressure Sensor that the PCM uses to calculate the difference between the vacuum in the system and the outside atmospheric pressure. Note that for this test to run successfully, the fuel tank must be between 25% and 85% full.

If leaks in vacuum lines, the charcoal canister, fuel cap, or any other component(s) are present, thus allowing outside air to enter the EVAP system during self-test cycles, the engine vacuum is unable to create, or maintain the vacuum required to test the system. When this happens, code P1457 is set, and a warning light may be illuminated.

The image below shows a simplified schematic of a typical EVAP system. Note that the vent control valve, which is normally open, is closed by the PCM during test cycles to create the vacuum required to run self-diagnostic tests.

What are the common causes of code P1457?

Possible causes of code P1457 could include the following-

• Defective vent valve
• Defective vent valve solenoid
• Defective, or loose fuel filler cap
• Damaged vacuum lines
• Damaged or corroded charcoal canister
• Damaged, burnt, shorted, or corroded wiring and/or connectors
• Open circuits
• Defective purge valve. In these cases, the purge valve could be stuck partially or even fully open, allowing outside air to enter the EVAP system through the normally open vent valve. Other codes, specifically codes referring to the purge valve and vapor flow/pressure are almost certain to be present along with P1457.
• Defective fuel tank pressure sensor. In these cases, codes referring to the fuel tank pressure sensor are likely to be present along with P1457.

What are the symptoms of code P1457?

In many cases, the only symptoms that are likely to be present are a stored trouble code and an illuminated warning light. Other possible symptoms could include rough idling or frequent engine stalling if a large vacuum leak exists between the intake manifold and the purge valve. If this symptom is present, it is likely that other fuel and air metering codes will be present along with code P1457.

Note however that if code P1457, or any other code that indicates a leak in the EVAP system is present, the vehicle may not pass an emissions test since the EVAP monitor may not have been able to complete all required tests.

How do you troubleshoot code P1457?

NOTE #1: Diagnosing code P1457 requires a repair manual that includes a pressure-to-resistance chart for the application, a good quality digital multimeter, a hand-held vacuum pump, and a smoke machine with which to identify small leaks in vacuum lines and other components.

NOTE #2: Performing a diagnostic procedure on the EVAP system is always easier if the vehicle is placed on a lift or hoist.

Step 1

Record all faults present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.

Step 2

Consult the manual to determine the function, routing, and location of all EVAP components, as well as all fuel and vacuum lines. Perform a thorough visual inspection of all lines, and check for damaged, pinched, dislodged, or cracked/split lines and/or connections that could allow outside air to enter the EVAP system. Replace all damaged vacuum lines with OEM replacements to avoid issues with leaks caused by poorly executed repairs.

NOTE #1: Pay particular attention to the vacuum line between the vent valve and the charcoal canister if the two components are not directly linked. This line is sometimes difficult to access, so do not assume that there are no leaks in this hose just because it may be difficult to inspect it properly.

NOTE #2: At this point, be sure to check the charcoal canister for signs of corrosion or other damage. Corrosion on a metal canister is a sure sign that the canister is defective; replace the canister if there is any doubt as to its serviceability. In addition, remove the canister and shake it about to listen for evidence that the charcoal charge has disintegrated; replace the canister if there are signs of charcoal pellets and/or dust anywhere in the EVAP system. Also, test the canister to see that no airflow through it is possible toward the vent valve; it should only be possible to achieve airflow away from the vent valve, thus, if there is a flow toward both sides of the canister, the canister’s check valve is defective, requiring that the canister be replaced.

Step 3

Clear all codes after repairs are complete, and operate the vehicle for at least one complete drive cycle to see if any codes return. If the code persists, perform a thorough visual inspection of all associated wiring and connectors; look for damaged, shorted, burnt, disconnected, or corroded wiring and connectors. Make repairs as required, but be aware that replacing wiring is always the better option.

Step 4

Clear all codes after repairs are complete, and operate the vehicle for at least one complete drive cycle to see if any codes return. If the code persists, prepare to perform reference voltage, ground, resistance, and continuity tests on all associated wiring, but be sure to disconnect all EVAP system wiring from the PCM during resistance and continuity checks to prevent damage to the controller.

NOTE #1: Pay particular attention to the vent valves’ control circuit. The vent valve is normally open to allow outside air to assist in the displacement of fuel vapors toward the engine, and since the signal to close this valve during test cycles derives from the PCM, be sure to check that all electrical values between the PCM and the vent valve fall within the manufacturers’ specifications to ensure that the valve solenoid receives full system voltage. Compare all obtained readings with the values stated in the manual, and replace the wiring between the valve and the PCM if any discrepancies are found.

NOTE #2: If all electrical values fall within specifications and the scanner being used has control functions, command the vent valve closed multiple times to ensure that there are no intermittent faults present. The scanner will indicate whether or not the solenoid responds to the signal input. If the scanner does not have control functions, remove both the vent valve and the fuel tank pressure sensor from the vehicle for further testing.

Step 5

With the vent valve removed, measure the solenoid’s internal resistance, and compare the obtained value with that stated in the manual. Replace the valve if the obtained reading does not fall within specifications.

If the solenoid’s resistance checks out OK, attach the vacuum pump to one opening. Consult the manual on the correct direct voltage to apply to the valve to close it; apply direct current to close the valve, and draw a vacuum that registers on the pump gauge. Provided the test equipment is not defective in any way, the vacuum should hold steady if the vent valve is functional. If the vacuum decays, no matter how slowly, the valve is defective and must be replaced.

At this point, it is also a good idea to test the resistance of the pressure sensor. Replace the sensor if its internal resistance does not agree with the value stated in the manual.

Step 6

If all electrical values, including those for the vent valve solenoid and pressure sensor, fall within specifications and the vent valve holds a vacuum, suspect a leak somewhere in the vacuum lines. Reassemble the EVAP system, and prepare to perform a smoke test of the entire EVAP system.

NOTE: To fill the entire system with smoke requires that the vent valve be closed, and the purge valve be opened to make it possible to fill the system with smoke. Attach the smoke machine to the system at the point where the vacuum line attaches to the inlet manifold, and either command the purge valve open with the scanner, or apply direct current to the purge valve to open it. Be sure however to consult the manual on the correct procedure to apply direct current to any circuit or component.

Step 7

Make sure that all protective covers and shields are removed to be able to see all vacuum lines and other EVAP system components, and allow the system to fill with smoke, but be aware that it can take about 60 seconds or longer in some cases.

Note that charcoal canisters have small vent holes, so seeing smoke issuing from this hole would be normal. However, some vacuum leaks are exceedingly small, and it might take a while before they reveal their presence. Nonetheless, do not assume that there are no vacuum leaks just because they don’t show up immediately- in some cases, it can take several minutes for smoke to appear from pinholes in vacuum lines.

NOTE: Pay particular attention to the area around the fuel filer cap during the smoke test. If any smoke, no matter how little, can escape past the cap, so can fuel vapors. Replace the cap if any smoke leaks past it.

Step 8

Long experience had taught that smoke (even smoke laced with dye that fluoresces under UV light), does not always reveal pinhole leaks, so if no leaks become evident, attach the vacuum pump to the EVAP system, and draw a vacuum, but be sure to check that the purge valve is still open, and the vent valve closed.

Assuming that the connection is secure and that the test equipment is not defective, the vacuum should hold steady for several minutes, if not almost indefinitely. If the vacuum decays (however slowly), one tried and trusted way to find the site of the leak is to use a length (about 18 inches or so) of garden hose as a stethoscope. Passing one end of the hose over the system lines and components magnifies the sucking sound; thus, listening at the other end might reveal small leaks that may not have been evident with the smoke method. Make repairs as required if any vacuum leaks are found.

Step 9

Clear all codes after all repairs are complete, and complete at least two drive cycles as specified by the manufacturer to see if the code returns. If the code does not immediately return, it is likely that an intermittent fault is present in the system. Be aware though that intermittent faults can be extremely challenging and time consuming to find and repair; in some cases, it might be necessary to allow the fault to worsen before an accurate diagnosis, and definitive repair can be made.

Codes Related to P1457

• P1452 – Relates to “Unable To Bleed – Up Vacuum in Tank”
• P1450 – Relates to “Unable To Bleed Up Fuel Tank Vacuum”

NOTE: Some manufacturers have assigned definitions to code P1457 that are not related to the fuel tank vacuum. Below are some examples-

• BMW – “Heated Catalyst Power Switch Temperature Sensor Electrical (Bank 1)”
• Honda – “Evaporative Emissions (EVAP) Control System Leakage (EVAP Canister System) EVAP”
• Mercedes – “Purge Solenoid Control System”
• Porsche – “A/C Compressor Control”
• Volkswagen/Audi/Volvo – “Exhaust gas temperature sensor 2 open / short to B +” (Battery Positive)
• GM – “Catalyst Heater Diagnostic”

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