Relay 'Circuit 87' ( Engine ) (P2505)

Relay 'Circuit 87' (Engine) (P2505) is a diagnostic trouble code (DTC) that indicates a problem with the power supply to the engine control module (ECM). The ECM is responsible for managing various aspects of the engine's performance, such as fuel injection, ignition timing, and emissions control. If the ECM does not receive adequate voltage from the relay 'circuit 87', it may not function properly or cause the engine to stall.

The relay 'circuit 87' is part of the power distribution center (PDC), which is a fuse box located under the hood of the vehicle. The PDC contains several relays and fuses that protect and distribute power to different components of the vehicle. The relay 'circuit 87' is activated by the ignition switch and provides power to the ECM and other devices, such as the fuel pump and the injectors.

The most common causes of relay 'circuit 87' (engine) (P2505) are:

- A blown fuse in the PDC

- A faulty relay 'circuit 87'

- A loose or corroded connector or wiring in the PDC or ECM

- A bad ignition switch or key

- A defective ECM

To diagnose and fix relay 'circuit 87' (engine) (P2505), you will need a scan tool, a multimeter, and a wiring diagram of your vehicle. Follow these steps:

1. Connect the scan tool to the OBD-II port under the dashboard and retrieve the DTCs from the ECM. If you see relay 'circuit 87' (engine) (P2505), proceed to step 2. If you see other codes related to the ECM, such as P0606 or P0607, you may have a faulty ECM and need to replace it.

2. Locate the PDC under the hood and check the fuse for relay 'circuit 87'. If the fuse is blown, replace it with a new one of the same rating and clear the DTCs from the ECM. If the fuse is not blown, proceed to step 3.

3. Check the relay 'circuit 87' for signs of damage or corrosion. You can test the relay by swapping it with another one of the same type in the PDC and seeing if the problem persists. If the relay is faulty, replace it with a new one and clear the DTCs from the ECM. If the relay is not faulty, proceed to step 4.

4. Check the connector and wiring for relay 'circuit 87' and ECM for signs of looseness, corrosion, or damage. You can use a multimeter to measure the voltage and resistance of each wire and compare it with the wiring diagram of your vehicle. If you find any abnormality, repair or replace the connector or wiring as needed and clear the DTCs from the ECM. If you do not find any abnormality, proceed to step 5.

5. Check the ignition switch and key for signs of wear or damage. You can test them by turning them on and off several times and seeing if they operate smoothly and consistently. If you find any problem, replace them with new ones and clear the DTCs from the ECM.

If none of these steps solve relay 'circuit 87' (engine) (P2505), you may have an intermittent issue that requires further investigation by a professional mechanic.