Understanding OBD2 Code P1470 on Your Audi
When your Audi’s check engine light illuminates and a scan tool reveals the generic OBD2 diagnostic trouble code (DTC) P1470, you are dealing with a specific fault within the vehicle’s Evaporative Emission Control (EVAP) system. Specifically, P1470 is defined as “Leak Detection Pump Circuit / Open”. This code is prevalent across many Audi models from the late 1990s through the 2010s, including the A4, A6, A8, Q5, and Q7. Unlike a simple gas cap warning, P1470 points to an electrical or functional failure of a critical component designed to test the fuel system’s integrity for vapor leaks. Ignoring this code can lead to a failed emissions test and, in some cases, subtle drivability issues.
The Role of the Leak Detection Pump (LDP) in Audi’s EVAP System
The EVAP system’s primary function is to prevent gasoline vapors from the fuel tank from escaping into the atmosphere. The Leak Detection Pump (LDP) is its self-diagnostic heart. It’s not just a simple pump; it’s an intelligent actuator used by the Engine Control Module (ECM) to pressurize the fuel system and check for leaks.
How the Audi Leak Detection Pump Works
During specific driving conditions (usually after a cold start with a warm engine and between 35-65 mph), the ECM initiates a leak test. The LDP, which contains a small electric motor, a pump diaphragm, and a built-in pressure switch, creates a slight vacuum in the EVAP system. The ECM monitors the pressure switch signal to see if the vacuum holds. A rapid loss of vacuum indicates a large leak (like a missing gas cap), while a slow decay indicates a small leak. Code P1470 is set when the ECM detects an unexpected electrical condition in the LDP’s control circuit, preventing this test from occurring.
Common Audi Models and Engine Codes Affected
Code P1470 is frequently encountered in Audis equipped with the following common engine families:
- 1.8T & 2.0T FSI/TFSI Engines: Found in Audi A4 (B6, B7, B8), A5, Q5.
- 2.8L & 3.0L V6 Engines: Common in Audi A6 (C5, C6), A8.
- 4.2L V8 Engines: Appears in Audi S4, A8, and Q7 models.
The LDP’s location varies but is often found near the charcoal canister, under the vehicle behind the rear axle, or in the engine bay.
Symptoms and Causes of P1470 in Audi Vehicles
A P1470 code may not always cause obvious drivability problems, but it will trigger the malfunction indicator lamp (MIL). Understanding the symptoms and root causes is key to an efficient diagnosis.
Primary Symptoms of a Faulty Leak Detection Pump Circuit
- Illuminated Check Engine Light (MIL): The most common and often the only symptom.
- Failed Emissions Inspection: The vehicle will not pass a state or local smog test with an active EVAP code.
- Other EVAP Codes: May appear in conjunction, such as P0440, P0441, or P0442, indicating a broader system leak or flow issue.
- Rough Idle (Less Common): In some cases, a severe vacuum leak induced by a stuck-open LDP can affect engine idle quality.
Root Causes of DTC P1470
The “Circuit/Open” definition points to electrical issues, but mechanical failures can also trigger it.
- Failed Leak Detection Pump: The internal electric motor burns out, the diaphragm ruptures, or the pressure switch fails.
- Open or Shorted Wiring: Corroded, broken, or pinched wires in the harness connecting the LDP to the ECM.
- Poor Electrical Connections: Corrosion or bent pins at the LDP connector or the ECM.
- Blown Fuse: A dedicated fuse for the LDP circuit may be blown.
- Faulty Engine Control Module (ECM): Rare, but a failed driver circuit within the ECM itself can cause this code.
Step-by-Step Diagnostic Procedure for Audi P1470
Proper diagnosis requires a quality OBD2 scanner, a digital multimeter (DMM), and, ideally, access to Audi-specific diagnostic software like VCDS (VAG-COM). Always consult a vehicle-specific repair manual for wiring diagrams and values.
Step 1: Preliminary Checks and Code Verification
Clear the fault code and perform a test drive. If P1470 returns immediately, it indicates a hard fault. If it only returns after several drive cycles, it may be intermittent. Visually inspect the LDP, its wiring harness, and connector for obvious damage, corrosion, or disconnection. Check the relevant fuse.
Step 2: Electrical Circuit Testing with a Multimeter
Disconnect the electrical connector from the LDP. With the ignition ON (engine off), use your DMM to check for:
- Power Supply (Pin 1 – typically Black/Blue wire): Should have battery voltage (~12V).
- Ground (Pin 2 – typically Brown wire): Check for continuity to chassis ground (less than 5 ohms).
- Control Signal (Pin 4 – typically Green/White wire): This is the ECM’s pulsed control. Testing requires an oscilloscope or activating output tests with VCDS.
A lack of power or ground indicates a wiring problem upstream.
Step 3: Testing the Leak Detection Pump Itself
If power and ground are good, test the pump motor. Using jumper wires from the battery, apply 12V and ground directly to the pump’s motor terminals (usually Pins 1 & 2). A functioning pump will make a distinct clicking or humming sound as it cycles. Do not apply power for more than a few seconds. No sound indicates a failed pump motor.
Step 4: Using VCDS for Advanced Diagnostics
VCDS is invaluable. Use the “Output Tests” function to activate the LDP directly and listen for operation. Monitor the “LDP Pump” and “LDP Switch” measuring blocks during a leak test. The pressure switch status should change as the pump is commanded. A lack of change with a confirmed working pump points to a faulty internal switch.
Repair Solutions and Cost Estimation
Once the faulty component is identified, the repair path becomes clear.
Replacing the Audi Leak Detection Pump
Replacement is straightforward. After disconnecting the battery, disconnect the electrical connector and the two vacuum hoses (note their positions!). Unbolt the mounting bracket, replace the pump, and reassemble. Use only high-quality OEM (e.g., Pierburg) or reputable aftermarket parts. A faulty LDP is the most common fix for P1470.
Repairing Wiring Harness Issues
For damaged wires, solder and heat-shrink tubing provide a permanent repair. Never use twist-on connectors in automotive environments. Ensure the repair is sealed from moisture.
Estimated Repair Costs
- DIY (Part Only): A new Leak Detection Pump costs between $80 and $250, depending on the model and brand.
- Independent Shop: Typically $250 to $450 for parts and labor.
- Audi Dealership: Can range from $400 to $700+ due to higher parts costs and labor rates.
Addressing a P1470 code promptly restores your Audi’s emissions compliance and ensures its onboard diagnostics are fully functional, keeping you informed of any other potential issues.