Diagnostic Aids

WARNING: This page is about a different car, the 1995 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.

Perform this test when directed by QUICK TEST procedure. This CIRCUIT TEST is intended to diagnose:

Wiring harness circuits (HO2S and PWR).

Fig 1: Identifying HO2S Circuit & Connector Terminals

HO2S CIRCUIT INFORMATION

Circuit

PCM Pin No.

⁽¹⁾ BOB Pin No.

Wire Color

HO2S

Green/Black

PWR

n/a

Blue/Yellow

HEATER

106

Black

⁽¹⁾	Rotunda Breakout Box (007-00033).

1) Check Power To HO2S Turn ignition off. Disconnect HO2S wiring harness connector. Turn ignition on. Measure voltage between HO2S harness connector PWR terminal and ground. If voltage is less than 10 volts, repair PWR circuit. If voltage is 10 volts or more, go to next step.

2) Check HO2S Ground Turn ignition off. Install Breakout Box (007-00033), leaving PCM disconnected. Leave HO2S wiring harness connector disconnected. Measure resistance between breakout box test pin No. 52 and HEATER terminal of HO2S harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair or replace circuit as necessary.

3) Check HO2S Circuit Turn ignition off. Leave HO2S wiring harness connector disconnected. Measure resistance between breakout box test pin No. 29 and HO2S terminal of HO2S harness connector. Resistance should be 5 ohms or less. Measure resistance between breakout box test pin No. 29 and ground. Resistance should be 10,000 ohms or more. If resistance is as specified, replace HO2S. If resistance is not as specified, repair or replace circuit as necessary.