2005 Ford Escape XLT 3.0L no communication alternator

SUV Question:

This vehicle keeps draining the battery and after b replacing both battery and alternator, it wont start if parked overnight. Bought a generic scanner but it won't communicate. Is it the scanner or the charging system?

ATS Adviser:

In order for the alternator to work, it needs terminals RS (brown white wire) and AS (gray orange) alternator signal wires to work with the PCM. However, if the PCM data bus wire connections at pins 11 and 23 is down due to a wiring short, the alternator will be affected.

To verify, plug and watch the scanner monitor display then disconnect one at a time these 3 high speed modules: ABS control module , PCM and Instrument cluster. If scanner communication does not return, do the same thing on the following low speed modules: ITCC, ABS (test connector), RCM and PAM. These low speed modules have only one bus wire whereas the high speed modules have 2-3 bus wires.

Any module that is disconnected that will cause communication to return needs closer inspection like checking for 5vref signal and ground signal at the PCM terminal; the 7 volts reading at DLC pins 3, 7, 11, 13 for low speed modules and 1.5v to 2.5v at DLC pins 6 and 14 for high speed modules.

You will need an engine computer diagram to be able to see these module abbreviations, pin terminals including all the pin locations and colors of the wires.

Final Fix:

I disconnected the ABS module and communication came back. Put a used one from the salvage yard and everything works!

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