O/D Light Flashing Solenoid Issue Ford Explorer $14 Fix No Tools

1, Attatch Car Diagnostic Instrument (CDI) to a cell phone holder to left side air vent.
2, Leave CDI plugged in, no need to ever remove, does not drain battery.
3, Set panel to 'Clear Codes'
4, When O/D light flashes press right middle button 3 times.
From DeepSeek;
Excellent diagnosis. You've hit on a classic and well-documented issue with the 1998 Ford Explorer (and many other Ford vehicles of that era). You are absolutely correct: the problem is very likely in the **computer itself**, specifically a failing component related to the transmission control circuit.

Here’s a detailed breakdown of what's happening, why, and exactly what to do.

The Core Problem: The Transmission Control Module (TCM)

In the 1998 Explorer, the TCM is **integrated into the Powertrain Control Module (PCM)**. The PCM is the vehicle's main computer, handling both engine and transmission management.

*The Fault:* A specific component inside the PCM fails — typically a *capacitor or a resistor* on the circuit board that controls the solenoid pack power supply (often called the "Main Control" or "Main Power" circuit).
*The Symptom:* This failure causes intermittent or complete loss of power to the transmission's solenoid pack. The solenoids themselves are fine, the wiring might be fine, but they aren't getting the correct signal/power from the computer.
*The Warning:* The flashing Overdrive (O/D) Off light is the transmission's "check engine light." It indicates the PCM has detected a fault in the electronic control system and has stored a diagnostic trouble code (DTC).
Common Diagnostic Trouble Codes (DTCs)

When you scan the computer (which you must do), you will likely find one or more of these codes:
*P0743:* Torque Converter Clutch (TCC) Solenoid Circuit Electrical
*P0750:* Shift Solenoid A (SSA) Circuit Malfunction
*P0755:* Shift Solenoid B (SSB) Circuit Malfunction
*P0760:* Shift Solenoid C (SSC) Circuit Malfunction
*P0765:* Shift Solenoid D (SSD) Circuit Malfunction
*P1747:* Pressure Control Solenoid (PC Sol) "A" Driver Open Circuit

*Key Point:* If you see *multiple solenoid circuit codes at once* (e.g., P0750, P0755, and P0743), it is a *near-certain indicator* that the problem is in the PCM, not in four separate solenoids or their individual wires.