Possible Explanations:
* Shop-Specific Code: It's possible this is a code created or used internally by a specific repair shop. They might have their own internal numbering system for tracking issues.
* Misinterpretation: The code may have been misread or incorrectly recorded. Double-check the source of the code.
* Non-OBD Code: The vehicle may be displaying a different type of code, perhaps from a separate system within the truck (like the body control module) rather than the powertrain control module (PCM) that OBD-I codes would come from.
* Aftermarket Device: If you are using a non-Ford specific OBD scanner, it may display codes differently than what a Ford-specific scanner would report.
To find the correct diagnostic trouble code(s):
1. Use a proper OBD-I scanner: Obtain a code reader specifically designed for OBD-I systems (as used in 1993 vehicles). Generic OBD-II scanners generally won't work on these older cars.
2. Check the owner's manual: Your owner's manual *might* have a section on diagnostic codes, though it's less likely to include the detail needed for such an obscure code.
3. Consult a Ford repair manual: A Haynes or Chilton repair manual for your specific year and model will have the most comprehensive information on diagnostic trouble codes for the 3.0L engine. This is your best bet for proper diagnosis.
Without a valid OBD-I code from a suitable scanner, pinpointing the problem is impossible. The "173-536" code needs to be verified or replaced with a proper DTC.
