For engine codes P1501 and P1502, "Fuel pump relay output stage" is a generic definition, and the exact cause depends heavily on the specific vehicle
. While some vehicles tie these codes to the fuel pump relay, others relate them to different components entirely, such as the throttle body or speed sensor. Here is a breakdown of what these codes can mean based on the vehicle and system involved:
Common meaning on some vehicles
On certain vehicle models, particularly older European makes, these codes may point to a fuel pump relay circuit malfunction.
- P1501: Indicates a fuel pump relay circuit malfunction.
- P1502: Indicates that the fuel pump relay circuit has an electrical short to a positive voltage source (short to plus).
Possible causes:
- A faulty fuel pump relay.
- A short in the wiring leading to the relay.
- A defective Engine Control Module (ECM).
Meaning on Ford trucks
For Ford trucks, particularly older models like a 2001 F-250, the definition of
P1501
is different.- P1501: Can indicate a problem with the Vehicle Speed Sensor (VSS) signal.
- Cause: An inconsistent or erratic signal from the VSS can be sent to the Powertrain Control Module (PCM), which can cause the engine to stall at specific RPMs.
Meaning on watercraft (Sea-Doo)
On some watercraft, like Sea-Doo models,
P1502
has a completely different meaning and is not related to the fuel system.- P1502: A fault code related to the Throttle Position Sensor (TPS).
- Cause: This could be due to a misaligned sensor, wear and tear, or faulty wiring in the throttle actuator control system.
Meaning on some Porsche models
On certain Porsche models, such as a 2000 Boxster S, the P1502 code is unrelated to the fuel pump and points to the throttle body.
- P1502: "Throttle Jacking Unit, Spring Test – Above Limit".
- Cause: Often triggered by a low or disconnected battery, it indicates an issue with the electronic throttle control system that may require recalibration.
Next steps for diagnosis
To correctly diagnose codes P1501 and P1502, it is crucial to consider the vehicle's make, model, and year.
- Check the owner's manual or a service manual. Consult the official documentation for the most accurate definition of P1501 and P1502 for your specific vehicle.
- Inspect the fuel pump relay and wiring. If the generic definition applies, start by inspecting the fuel pump relay for corrosion or other damage. Then, test the wiring for shorts or open circuits.
- Perform manufacturer-specific tests. If the codes are not related to the fuel pump relay, research the appropriate diagnostic tests for the component indicated by the codes for your vehicle.
- Test the component. Replace or repair the component indicated by the codes, whether it's the VSS, TPS, or the ECM.
