This guide provides a detailed overview of the 04 Ford Explorer OBDII pinout, focusing on unnecessary wires and circuits that can be removed during an engine swap or conversion. This information is particularly useful for those integrating a different transmission or simplifying the engine management system.
Unnecessary C115 Connector Wires
The C115 connector often contains wires that are not required for certain engine swap configurations. While pin numbers can vary, one constant is pin #33. If a red/white wire occupies pin 33, it can be removed from both sides of the C115 connector as it’s typically associated with the transmission harness and not essential for engine operation.
Other wires within the C115 connector related to the Neutral Safety Switch (NSS) and reverse lights include:
- Pink: NSS input (start signal from the ignition switch).
- Red/Blue (96-97) or Tan/Red (98+): NSS output (start signal to the starter solenoid).
- Purple/Orange: Reverse light switch input (should be connected to a fused 10-amp power source).
- Black/Pink: Reverse light switch output (powers the reverse lights).
If you’re not using the 4R70W transmission, all these wires can be safely removed. If you are using the 4R70W, you can retain them and route them into the cab or remove them from the transmission harness if those circuits already exist in your body harness.
Removable PCM Pins
Several Powertrain Control Module (PCM) pins can be removed if their corresponding functions are not required. Remember to verify the pin usage in your specific harness and consult footnotes before removing any wires. Any PCM wires not explicitly listed here MUST be retained.
EVAP System
The Explorer’s Evaporative Emission Control (EVAP) system is complex. While not recommended for retention in most swaps due to its intricate setup, simplification is possible by converting it to a Fox Mustang-style system using a single purge valve. This modification allows for wiring pin 56 (Light Green/Black) to the purge solenoid and a switched 12V source. However, this approach has not been extensively tested in vehicles.
Removable EVAP-related pins:
- 12 – Yellow/White
- 56 – Light Green/Black
- 62 – Red/Pink
- 67 – Purple/White***
Air Conditioning (A/C)
The A/C system can be wired to bypass PCM control, eliminating wide-open throttle (WOT) A/C cutoff. This allows for continuous A/C operation. The A/C input can alternatively be used for a high idle switch.
A/C related pins and their modified functions:
- 41 – Dark Green/Orange or Purple*** (A/C or High Idle On signal) Connect to a switched 12V source when A/C or high idle is desired.
- 69 – Pink/Yellow (PCM controlled A/C relay) – Removed in this modified setup.
- 86 – Black/Yellow – Grounded in this setup for A/C or high idle functionality.
*** On later harnesses where pin 41 is purple, pin 67 (Purple/White) can be used instead to avoid color duplication.
Exhaust Gas Recirculation (EGR)
If the EGR system is not used, the following pins can be removed:
- 47 – Brown/Pink +++ (Resistor location for 96 harnesses when removing EGR)
- 63 – Orange/Yellow
- 65 – Brown/Light Green
Miscellaneous Unused Pins
These pins can generally be removed:
- 14 – Light Blue/Black
- 19 – Orange/Black
- 43 – Light Blue/Pink
Essential 4R70W Transmission and Rear O2 Sensor Pins
The following pins are essential for the 4R70W transmission and rear O2 sensors and should NOT be removed if these components are used: (refer to the original document for a comprehensive list)
4R70W Transmission Swap Considerations
When swapping a 4R70W transmission between different model years (e.g., using a 98+ transmission in a 96-97 vehicle), ensure compatibility between the transmission range sensor and the PCM. Additionally, repin the transmission connector to match the year of the transmission. For 98+ transmissions in earlier vehicles, this typically involves removing two unused power wires.
Vehicle Speed Sensor (VSS) Considerations
Refer to the flowcharts below to determine if the VSS is required for your specific application:
This guide provides a foundation for understanding the 04 Ford Explorer OBDII pinout and identifying unnecessary circuits. Always double-check your specific wiring diagrams and exercise caution when modifying your vehicle’s electrical system.
