pin point test
Post Fiend
Joined: Jan 2003
Posts: 9,748
Likes: 16
From: Connecticut
Fuel Pump Circuit & Code 95
This isn't a pinpoint test, but it might help you get a better idea of what you are dealing with:
The FP electrical circuit has a fuel pump control relay controlled by the powertrain control module (PCM), which provides power to the fuel pump under various operating conditions. When the ignition switch in the OFF position, the contacts of the PCM power and fuel pump relays are open.
When the ignition switch is first turned to the ON position, the PCM power relay is energized, closing its contacts. As a result, power is provided to both the fuel pump relay and a timing device in the powertrain control module. The fuel pump runs through the contacts of the fuel pump relay and the inertia fuel shutoff switch . If the ignition switch is not turned to the START position, the timing device in the powertrain control module will open the relay ground circuit to the relay after approximately one second.
Opening the ground circuit de-energizes the fuel pump relay (opening its contacts), which turns the fuel pump off. This circuitry provides for pre-pressurization of the fuel system.
When the ignition switch is turned to the START position, the powertrain control module grounds the fuel pump relay to provide fuel for starting the engine while cranking.
After the engine starts, the ignition switch is returned to the ON position, and power to the fuel pump is again supplied through the fuel pump relay. The powertrain control module senses engine speed and shuts off the fuel pump by opening the ground circuit to the fuel pump relay when the engine stops or is below 120 rpm.
DTC 95/542 indicates that one of the following has occurred:
No Start:
- Inertia Fuel Shutoff (IFS) switch not reset or electrically open (if in secondary circuit).
- Open circuit between the fuel pump and FPM circuit connection to the power-to-pump circuit.
- Poor fuel pump ground.
- Fuel pump electrically open.
Engine Starts:
- Fuel pump secondary circuit short to power.
- Fuel pump relay contacts always closed.
- Open in FPM circuit between PCM and connection to the power-to-pump circuit.
- Left/front HO2S short to power (dual HO2S applications).
- Damaged Powertrain Control Module (PCM).
The FP electrical circuit has a fuel pump control relay controlled by the powertrain control module (PCM), which provides power to the fuel pump under various operating conditions. When the ignition switch in the OFF position, the contacts of the PCM power and fuel pump relays are open.
When the ignition switch is first turned to the ON position, the PCM power relay is energized, closing its contacts. As a result, power is provided to both the fuel pump relay and a timing device in the powertrain control module. The fuel pump runs through the contacts of the fuel pump relay and the inertia fuel shutoff switch . If the ignition switch is not turned to the START position, the timing device in the powertrain control module will open the relay ground circuit to the relay after approximately one second.
Opening the ground circuit de-energizes the fuel pump relay (opening its contacts), which turns the fuel pump off. This circuitry provides for pre-pressurization of the fuel system.
When the ignition switch is turned to the START position, the powertrain control module grounds the fuel pump relay to provide fuel for starting the engine while cranking.
After the engine starts, the ignition switch is returned to the ON position, and power to the fuel pump is again supplied through the fuel pump relay. The powertrain control module senses engine speed and shuts off the fuel pump by opening the ground circuit to the fuel pump relay when the engine stops or is below 120 rpm.
DTC 95/542 indicates that one of the following has occurred:
No Start:
- Inertia Fuel Shutoff (IFS) switch not reset or electrically open (if in secondary circuit).
- Open circuit between the fuel pump and FPM circuit connection to the power-to-pump circuit.
- Poor fuel pump ground.
- Fuel pump electrically open.
Engine Starts:
- Fuel pump secondary circuit short to power.
- Fuel pump relay contacts always closed.
- Open in FPM circuit between PCM and connection to the power-to-pump circuit.
- Left/front HO2S short to power (dual HO2S applications).
- Damaged Powertrain Control Module (PCM).
