Powertrain Controls - ECM/PCM

A/D Multiplexer Chip:

Circuit Description:
The A/D multiplexer chip is an internal part of the PCM. The above exploded view SFI-U PCM shows sensor inputs to the A/D multiplexer that can affect driveability and diagnostics.

DTC 86 Will Set When:
Any of the above circuits is shorted to system voltage for 15 seconds.

Action Taken (PCM will default to):
The MIL will become illuminated.

DTC 86 Will Clear When:
A current DTC 86 will clear when 12 volts is no longer sensed on the above circuits. A history DTC 86 will clear after 50 consecutive ignition key cycles without a current DTC 86 being stored.

Diagnostic Aids:
If DTC 86 is not present, all circuits leading to the PCM that are connected to the A/D multiplexer should be checked for an intermittent short to B+ Move the harnesses of each component and watch the scan data on the Tech 1. The circuit that is shorted to B+ will show erratic changes in data on the Tech 1.

For DTC 86, check for any DTCs that are stored and refer to those charts. If no other DTCs are stored, check all PCM connectors and terminals for proper location. DTC 86 will set only when the circuits leading to the A/D multiplexer, internal to the PCM gets shorted to B+.