Circuit Test STP - Switch To Power: Notes

WARNING: This page is about a different car, the 1994 Mercury Tracer and 1994 Ford Escort. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Switch Circuit & Conn. Terminal ID (STP - 1.8L 3 & 5 Door)

Fig 2: Switch Circuit & Conn. Terminal ID (STP - 1.8L 4-Door)

Fig 3: Switch Circuit & Connector Terminal ID (STP - 1.8L)

NOTE: Enter this test only when directed here from SWITCH MONITOR TEST. This test is intended to diagnose following switches and circuits: Brake On-Off (BOO) switch, Headlight (HDLT) switch, Rear Window Defrost (DEF) and Vehicle Start (VST) switch.

CIRCUIT PIN IDENTIFICATION

Circuit	Breakout Box Pin No.	PCM Pin	Wire Color
A/T
BOO	2	1Q	Green
DEF	34	1J	Black/Blue
HDLT	32	1H	Red/Black
VST	5	1C	Purple
M/T
BOO	2	1O	Green
DEF	30	1T	Black/Blue
HDLT	28	1U	Red/Black
VST	5	1C	Purple

1) Check System Integrity Visually check all wiring, connectors and components for damage, shorting or looseness. If fault is found, repair as necessary. If no fault is found, go to next step.

2) Check Switch Signal To PCM Turn ignition off. Install breakout box, leaving PCM disconnected. Turn ignition on. Measure voltage between breakout box test pin of switch being tested and ground. Check voltage with switch in ON (closed) and OFF (open) positions. See SWITCH PERFORMANCE CHECK. If voltage is as specified and no other problem or code is found, perform CIRCUIT TEST SML. If SML is okay, replace PCM. On headlight switch, if voltage is not as specified but headlights work, check for open wire. If headlights do not work, test headlight switch. See STEERING COLUMN SWITCHES article in ACCESSORIES/SAFETY EQUIPMENT section below. On all other switches, if voltage is not as specified, go to next step.

3) Check Power To Switch Turn ignition off. Disconnect connector of switch to be tested. Turn ignition on. Measure voltage at PWR terminal of switch. If voltage is about battery voltage, go to next step. If voltage is less than battery voltage, repair open PWR wire.

4) Check Switch Continuity Turn ignition off. Disconnect connector of switch to be tested. Measure resistance between switch terminals. Resistance should be less than 5 ohms with switch closed and more than 10,000 ohms with switch open. If resistance is not as specified, replace switch. If resistance is as specified and no other problem or code is found, replace PCM.