P0443 Evaporative Emission Control System Purge Valve Circuit

OBD-II Trouble Code - P0443 - Data Sheet

Purge valve circuit of the fuel vapor control system.

P0443 is a generic OBD-II code indicating that the engine control module (ECM) has detected a malfunction in the purge control valve or its control circuit. This may indicate an open or short circuit in a valve or circuit.

What does trouble code P0443 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.

The EVAP (vapor recovery system) allows the exhaust gases from the gas tank to enter the engine for combustion, rather than being discharged into the atmosphere. The purge valve solenoid supplies switched battery voltage.

The ECM controls the valve by operating the ground circuit by opening the purge valve at a specific time, allowing these gases to enter the engine. The ECM also monitors the ground circuit for faults. When the purge solenoid is not activated, the ECM should see a high ground voltage. When the solenoid is activated, the ECM should see that the ground voltage is lowered to near zero. If the ECM does not see these expected voltages or detects an open circuit, this code will set.

Note. This DTC is the same as P0444 and P0445.

Possible symptoms

DTC P0443 symptoms may simply be the Malfunction Indicator Lamp (MIL) illuminated. There may not be any problems with handling. But a lean mixture or rough engine operation is also possible if the purge valve is stuck open. However, these symptoms are usually accompanied by other EVAP codes. Another sign may be increased pressure in the gas tank as a "whistling" sound when the cap is removed, indicating that the purge valve is not working or is stuck closed.

• The Check Engine light will come on and the code will be stored in the ECM.
• You may notice a slight decrease in fuel consumption if the vapor recovery system is not working.

Causes of the P0443 code

• The ECM has commanded the purge control valve to open and has detected either an incomplete open circuit or a short in the circuit.
• The P0443 code could be caused by an internal open circuit in the purge control valve or a corroded connector causing the valve to lose contact.
• The code can also set if the wiring to the valve is damaged between the ECM and the purge valve, causing an open circuit if the wire is cut, or a short circuit if the wire is shorted to ground or power.

There must be a purge control problem to trigger the P0443 code. CHAINnot necessarily a valve. Usually they are a block in which the valve and solenoid are assembled. Or it can consist of a separate solenoid with vacuum lines to the purge valve. However, it can be any of the following:

• Defective purge solenoid (internal short circuit or open circuit)
• Rubbing the wiring harness or rubbing another component causing a short or an open in the control circuit
• Connector worn, broken, or shorted due to water ingress
• The driver circuit inside the powertrain control module (PCM) is defective

Possible solutions

1. Using a scan tool, command the purge solenoid to activate. Listen or feel the purge solenoid click. It should click once, and on some models it may click again.
2. If no click occurs when the scan tool is activated, disconnect the connector and check the solenoid and connector for damage, water, etc. Then check for battery voltage on the lead wire with the key on. If you have battery voltage, manually ground the control panel with a jumper wire and see if the valve clicks. If so, then you know the solenoid is working properly, but there is a problem with the control circuit. If it does not click when manually grounded, replace the purge solenoid.
3. To test for a problem in the control circuit (if the solenoid is running normally and you have voltage at the solenoid), reconnect the solenoid and disconnect the control circuit (ground) wire from the ECM connector (if you don't know how to do this, don't try). With the ground wire disconnected from the ECM, turn on the key and manually ground the purge valve control wire. The solenoid should click. If so, then you know there is no problem with the control wire to the solenoid and there is a problem with the ECM purge solenoid drive circuit in the ECM. You will need a new ECM. However, if it does not click, then there must be an open in the wiring between the ECM and the solenoid. You must find it and repair it.

Other EVAP System DTCs: P0440 - P0441 - P0442 - P0444 - P0445 - P0446 - P0447 - P0448 - P0449 - P0452 - P0453 - P0455 - P0456

How does a mechanic diagnose a P0443 code?

• Scans codes and documents code in ECM, looks at freeze frame data to see when an error occurred
• Inspects all wiring and the vapor purge valve system, including the purge valve connector for corrosion, damaged or loose connections or wires.
• Checks the purge valve vent valve for clogging with dirt, debris, or cobwebs.
• Performs a smoke leak test on the fuel vapor system to attempt to determine the cause of a vapor leak using the vapor inspection port.
• Checks the purge control valve for proper valve resistance and then checks valve operation using the ECM to control the valve.

Common Mistakes When Diagnosing Code P0443

• Do not check and assume that the purge control valve is faulty without doing a thorough diagnosis of the entire system to later discover if the wiring is broken or cut.
• Do not troubleshoot and replace parts that may or may not be the problem

How serious is the P0443 code?

• A P0443 code causes the check engine light to come on and this alone will result in a failed emissions test.
• This code means that the EVAP control valve is defective or the circuit to it is not connected to the valve, so the ECM has lost control of the valve.
• The vapor recovery and reuse system, if not working properly, can result in loss of fuel consumption.

What repairs can fix code P0443?

• Checking and replacing the purge control valve
• Repairing damaged wiring to the blowdown control valve and preventing re-damage
• Purge valve replacement

Additional comments to consider regarding code P0443

Code P0443 is a fairly common code that cars come with today that causes the check engine light to come on. The most common cause is that the fuel tank cap was accidentally removed or loosened after filling with fuel. For this code, the most common fault is that the purge control valve has an internal open circuit or the bleed valve is not holding vapor.

How to Fix P0443 Engine Code in 3 Minutes [2 DIY Methods / Only $4.53]

Need more help with your p0443 code?

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