KF - Testing Notes

DESCRIPTION
The Powertrain Control Module (PCM) determines engine cooling fan requirements and controls the fan operation through the Low Fan Control (LFC) and High Fan Control (HFC) outputs. The HFC relay is a normally open relay. The LFC relay is normally open.

Both Fans Off
The HFC and LFC output are off.

Low Speed Fan On
The LFC output is turned on closing the normally open LFC relay. The HFC output is off, and B(+) is supplied to the LFC relay through the HFC relay.

High Speed Fan On
The HFC output is on which closes the HFC relay. With the HFC relay contacts closed, B(+) is not supplied to the LFC relay preventing both fan speeds from being activated at the same time.

NOTE
You should enter this Pinpoint Test only when you have been directed here from Diagnostic Routines,

REMEMBER
This Pinpoint Test is intended to diagnose only the following:

- Harness circuits: LFC, HFC, LFC Power-To-Fan, HFC Power-To-Fan, IGN Start/Run and GND.

- LFC Relay

- HFC Relay

- Cooling Fan

- PCM