2007 GMC Envoy P2431 Code: Secondary Air Injection System Air Flow/Pressure Sensor Circuit Range/Performance Diagnosis and Fix

The P2431 code typically points to a faulty air pressure sensor within the secondary air injection system. Possible root causes include: - Defective secondary air pump - Faulty one-way check valve - Malfunctioning air control solenoid valve - Damaged or defective air pressure sensor - Corroded, damaged, or loose wiring connections - Failed Powertrain Control Module (PCM) For accurate diagnosis, voltage and resistance tests using a digital multimeter (DMM) are recommended. A scan tool can also provide real-time data to confirm system behavior.

If the system appears to function normally during operation, a defective air pressure sensor is likely. The sensor is typically a three-wire potentiometer with a 5V reference signal and ground. Circuit testing using a DMM should be performed while monitoring valve position (open/closed). If the diverter valve is stuck closed or the pump runs continuously under load, it may damage internal components. Some pumps have built-in thermal cutoffs that activate when overheated — verify this behavior during operation.

I applied 12V directly to the diverter valve and heard a clear click. When I started the engine cold, I removed the hose from the diverter and observed air flow for about 10 seconds — this confirms that the pump is functioning properly.

A clicking sound does not necessarily mean the valve is opening or closing — relays and solenoids can remain stuck closed internally. The PCM monitors feedback from the position sensor and may detect abnormal readings, indicating a failure in the sensor itself (within the solenoid assembly) or wiring between the sensor and PCM. Circuit testing with a DMM is essential to verify whether the solenoid opens properly. In many cases, components pass resistance tests but fail to operate due to internal defects — this is especially common in older GM vehicles.

I will retest the air solenoid and perform additional diagnostics to confirm its operation.

After removing the diverter valve, I visually inspected it. The inlet shows clear movement — it opens and closes when voltage is applied. This confirms mechanical functionality of the valve itself. However, I'm still unsure whether air should be flowing continuously to the diverter under normal conditions.

I tested the solenoid by applying battery voltage (12V) to pin 6 (purple wire) and grounding pin 4 (black wire). The valve fully opened. Is this correct? Do you have a digital multimeter? When powered with both purple wire and constant ground, the solenoid should open completely. If it doesn’t, the issue may lie in the internal feedback mechanism or wiring between the sensor and PCM.

The PCM only activates the pump briefly during cold starts to allow the catalytic converter to warm up. For accurate diagnosis, voltage testing on the potentiometer circuit using a DMM is highly recommended — this will reveal whether the sensor is providing correct feedback.

Using a scan tool to monitor live data PIDs is the most effective diagnostic method. The three-wire pressure sensor sends a voltage signal (typically around 2.5V on yellow wire) to the PCM. The PCM converts this into air pressure and compares it with barometric readings. During pump operation, the signal should rise to approximately 3.10 volts. A piercing probe or back-probe is needed to access these signals directly — this is one of the most common failure points in GM vehicles.

Thank you for the detailed guidance — it's very helpful.

Without a scan tool, diagnosing this issue is challenging. First, verify that the 5V reference wire has proper voltage using a DMM (connect between the 5V wire and ground). A stable 5V reading indicates good wiring and power supply. Then test for continuity and signal integrity on the signal wire — use a piercing probe or back-probe to check voltage at both the sensor and PCM. The pump should only run for 4–5 seconds when cold; if it runs longer, there may be an issue with the control circuit. Have you cleared the code and observed whether it returns? This suggests whether the fault is intermittent or permanent.

I disassembled the diverter valve yesterday and found significant carbon buildup. I cleaned it thoroughly and applied WD-40 to the shaft. After clearing the code, I drove around for a short distance — the P2431 code did not return. I will continue driving today to monitor if the issue reappears.

I used carb cleaner in the past to clean GM idle air control stepper motors — hope that helped with your diverter valve. Unfortunately, modern OEM parts are increasingly prone to failure. I always recommend replacing components rather than cleaning them due to long-term reliability concerns. Please let me know how it turns out.

I replaced the diverter valve with a new one and reset the codes on Tuesday. The P2431 code has not returned — all systems are now functioning normally. Thank you for your support!

Great to hear it's resolved! Thanks for sharing your experience — this helps others facing the same issue.