Understanding the P1472 OBD2 Code in Chevrolet Vehicles
The OBD2 diagnostic trouble code P1472 is a manufacturer-specific code primarily associated with General Motors (GM) vehicles, including Chevrolet models like the Silverado, Tahoe, Suburban, and Express vans. In simple terms, this code indicates a malfunction within the Evaporative Emission Control (EVAP) system, specifically pointing to the “EVAP Purge Pump Control Circuit.” Unlike generic EVAP codes, P1472 is a more targeted alert, signaling that the vehicle’s Powertrain Control Module (PCM) has detected an electrical issue with the circuit controlling the EVAP leak detection pump or purge pump. This system is critical for preventing fuel vapors from escaping into the atmosphere and must be addressed to pass emissions tests and ensure optimal engine performance.
What is the EVAP System and the Purge Pump?
The EVAP system is designed to capture fuel vapors from the gas tank and temporarily store them in a charcoal canister. During specific engine conditions, the PCM commands a purge valve to open, allowing these stored vapors to be drawn into the engine’s intake manifold and burned. In many modern GM/Chevrolet applications, a dedicated EVAP leak detection pump (also called a purge pump) is used. This pump creates a vacuum to pressurize the EVAP system, allowing the PCM to monitor for leaks. The P1472 code directly concerns the electrical pathway that the PCM uses to command this pump on and off.
Technical Definition of Code P1472
According to GM service information, P1472 is defined as: “EVAP Purge Pump Control Circuit.” This means the PCM has seen a voltage level on the control circuit that is outside its expected normal operating range. This could be a voltage that is too high (open circuit) or too low (short circuit) when the pump is being commanded. The PCM monitors this circuit for rationality and flags P1472 when the actual electrical feedback does not match its commanded state.
Common Symptoms and Causes of P1472 in Chevrolet
While the EVAP system is not directly tied to engine power, a malfunction indicated by P1472 can lead to noticeable issues. The most immediate symptom is the illumination of the Check Engine Light (MIL) on your dashboard. Since the code is related to the leak detection cycle, you will likely fail a state emissions inspection. In some cases, you may also notice a slight decrease in fuel economy, as the engine management system may enter a conservative fuel trim strategy.
Primary Causes of the P1472 Code
- Faulty EVAP Leak Detection / Purge Pump: The most common culprit. The internal motor or solenoid within the pump itself can fail.
- Open or Shorted Wiring: Damaged, corroded, or broken wires in the pump’s control circuit or its power/ground connections.
- Poor Electrical Connections: A corroded, loose, or damaged connector at the pump or PCM.
- Blown Fuse: A dedicated fuse supplying power to the EVAP pump circuit may be blown.
- Faulty Powertrain Control Module (PCM): While rare, a malfunction within the PCM itself can cause it to incorrectly read the circuit. This should be diagnosed only after all other possibilities are eliminated.
Vehicle Models Commonly Affected
Code P1472 is frequently encountered in Chevrolet and GMC trucks and SUVs from the early 2000s to the 2010s that utilize a dedicated leak detection pump. This includes popular models such as:
- Chevrolet Silverado (1500, 2500, 3500)
- Chevrolet Tahoe
- Chevrolet Suburban
- Chevrolet Avalanche
- GMC Sierra
- GMC Yukon
- Chevrolet Express Vans
Step-by-Step Diagnostic Procedure for P1472
Diagnosing P1472 requires a systematic approach, starting with the simplest checks and moving toward more complex tests. You will need a quality OBD2 scanner capable of reading manufacturer-specific codes, a digital multimeter (DMM), and basic hand tools. Always consult the vehicle’s specific service manual for wiring diagrams and connector locations.
Step 1: Preliminary Inspection and Code Verification
Begin by clearing the code with your scanner and performing a short test drive. If P1472 returns immediately, it indicates a hard fault. If it takes several drive cycles, it may be intermittent. Next, perform a thorough visual inspection:
- Locate the EVAP leak detection pump (often near the charcoal canister under the vehicle or in the engine bay).
- Inspect all associated wiring harnesses for obvious damage, chafing, or rodent chewing.
- Check the electrical connector at the pump for corrosion, bent pins, or loose fit.
- Verify the condition of the related fuse in the under-hood fuse box.
Step 2: Electrical Testing of the Pump and Circuit
With the vehicle’s ignition OFF, disconnect the electrical connector from the EVAP pump. Using your multimeter, check the pump’s resistance across its terminals (refer to service manual for specs; typical range is 10-30 ohms). An infinite reading (open) or a very low reading (short) confirms a bad pump. Next, with the connector still disconnected and the ignition ON, use the DMM to check for battery voltage at the power wire in the harness connector. Also, check for a good ground by testing continuity between the ground wire pin and a known good chassis ground.
Step 3: Checking the PCM Control Signal
This test often requires a scan tool with bidirectional controls or an advanced multimeter. Using the scanner, you can often command the EVAP pump ON and OFF while monitoring the control circuit voltage or listening/feeling for the pump to activate. If the scanner command does not change the voltage state at the pump connector (or a test light doesn’t illuminate), the issue lies in the control circuit wiring or the PCM itself. A wiring diagram is essential here to perform continuity tests between the pump connector and the PCM connector.
Repair Solutions and Prevention Tips
Once the root cause is identified, the repair is typically straightforward. The goal is to restore proper electrical integrity to the EVAP purge pump control circuit.
Common Repairs for P1472
- Replacing the EVAP Leak Detection Pump: If the pump fails the resistance test, replacement is necessary. Use a high-quality OEM or reputable aftermarket part.
- Repairing Wiring Harness: For damaged wires, solder and heat-shrink the repair. Never use twist-on connectors for automotive wiring repairs.
- Cleaning or Replacing Connectors: Use electrical contact cleaner and a small brush to clean corroded terminals. If damaged, replace the connector pigtail.
- Replacing a Blown Fuse: Always investigate why a fuse blew—it is usually a symptom of a short circuit elsewhere.
Post-Repair Procedure and Prevention
After completing the repair, clear all diagnostic trouble codes with your OBD2 scanner. Perform a complete drive cycle to allow the PCM to run all its self-tests, including the EVAP leak detection monitor. Verify that the Check Engine Light remains off and that the code does not return. To prevent future issues, avoid pressure washing the engine bay directly near electrical connectors and routinely inspect undercarriage components for damage if you drive on rough terrain.
Addressing a P1472 code promptly not only ensures your Chevrolet complies with emissions regulations but also maintains the efficiency and reliability of your vehicle’s fuel evaporation management system. By following this technical guide, you can diagnose and resolve this common GM-specific fault with confidence.