How does a Chrysler leak detection pump work?
The leak detection pump (LDP) in many Chrysler vehicles is a small electric motor that creates a controlled vacuum in the evaporative emissions system to allow the powertrain control module (PCM) to test for leaks. This pump is a key part of the EVAP system’s self-diagnostic routine.
In more detail, Chrysler’s LDP works in concert with the charcoal canister, purge valve, vent valve, and EVAP pressure sensor. The PCM commands the LDP to perform a leak test under specific operating conditions, isolates the EVAP canister from the engine and atmosphere, and monitors how the vacuum behaves. If the system fails to hold vacuum or shows an abnormal rate of change, the PCM flags a fault code indicating a potential leak in hoses, the canister, the tank, or related components.
Role and mechanism of the leak detection pump
Before outlining the steps of the test, here is how the LDP participates in Chrysler’s evaporative emissions diagnostics.
- The PCM schedules an EVAP self-test and activates the LDP to evacuate air from the EVAP circuit, creating a defined vacuum.
- Valves in the EVAP system (purge and/or vent) are commanded to seal the canister from the atmosphere and engine, turning the test into a sealed-leak scenario.
- The LDP maintains or builds vacuum while the ECM monitors the EVAP pressure sensor reading to establish how quickly pressure changes occur.
- If the vacuum holds within expected limits, the PCM considers the test passed; if the vacuum decays too quickly or cannot be established, a leak is suspected and a diagnostic trouble code is set.
In practice, the LDP’s job is to provide a repeatable, known vacuum source for the EVAP system so the PCM can determine whether there are leaks anywhere in the tank, hoses, canister, or purge paths.
Location and signs of trouble
Where the LDP is typically found
In many Chrysler models, the LDP is a compact pump assembly mounted near the EVAP canister, which is usually located in the engine compartment or behind the rear bumper area depending on the model. It is integrated into the EVAP canister assembly or adjacent lines and connections.
Common symptoms and failure indicators
- Check Engine Light with EVAP-related codes (for example P0440, P0442, P0455 or similar, depending on model year and region).
- Persistent or intermittent EVAP leaks detected during scan-tool readiness tests or emissions testing.
- Audible buzzing or abnormal pump noise near the EVAP canister area when the system runs a test.
- Cracked hoses, loose clamps, or damaged canister components observed during inspection.
Conclusion: If the LDP or its associated valves and lines fail, the EVAP system may not be able to complete its leak-detection test, triggering codes and potentially failing an emissions test.
Diagnostics and repair path
Before delving into the repair steps, technicians typically verify the issue with a structured diagnostic approach to avoid unnecessary part replacement.
- Scan the vehicle for EVAP-related fault codes and check the readiness status of the EVAP system.
- Visually inspect the EVAP hoses, the canister, purge and vent valves, and the LDP wiring for damage, wear, or poor connections.
- Perform a pressure/volume test or a smoke test to identify exact leak locations and verify whether the LDP can create and maintain vacuum as commanded.
- Test the LDP electrical circuit (power, ground, and control signal) to confirm the pump receives proper commands from the PCM.
- Replace the faulty component—often the LDP assembly, but sometimes the purge valve, vent valve, or damaged hoses may be the actual leak source. In some cases, the entire EVAP canister needs replacement.
Concluding: Accurate repair hinges on confirming whether the leak originates from the LDP itself or from allied EVAP components, followed by replacement of the faulty part and re-testing to ensure the system is sealed.
What Chrysler owners should know
Owners with EVAP codes should rely on OEM service information and appropriate diagnostic tools. A dealership or qualified mechanic can perform the manufacturer’s EVAP readiness tests, run the LDP leak test, and execute a smoke test to pinpoint leaks. Repair decisions should consider the entire EVAP pathway, including hoses, clamps, the canister, purge/vent valves, and the LDP unit itself.
Summary
The Chrysler leak detection pump is a small electric device that creates a controlled vacuum in the evaporative emissions system to enable a deliberate leak-detection test. Working with purge and vent valves and an EVAP pressure sensor, the LDP lets the PCM determine whether there are leaks in the fuel vapor system. If the test detects a leak, fault codes are issued and the EVAP components—often the LDP itself or related hoses/valves—are inspected and replaced as needed. A precise diagnosis, typically with OEM diagnostic tools, is essential for a reliable repair and a clean emissions performance.
