Brake On/Off (BOO) Switch

1996 PCED OBDI

SECTION 18: Diesel Diagnosis — 7.3L DI Engine

K: Brake On/Off (BOO) Switch

K1 DIAGNOSTIC TROUBLE CODE (DTC) 0703: CHECK PID "BOO" WITH NGS TESTER

Note: When performing KOER switch test, wait five seconds after pressing the trigger to start the test before running through the driver operated controls. The test may also take up to five minutes to complete.

No PID transition indicates a BOO circuit failure.
Key on, engine off.
Firmly cycle brake pedal.

Does PID read ON only?

Yes	No
GO to K2.	GO to K4.

K2 CHECK FOR BOO SWITCH FAILED CLOSED

Key on, engine off.
Unplug BOO switch.

Does PID go to OFF?

Yes	No
REPLACE BOO switch. CONFIRM fix with NGS Tester PID "BOO" and with stoplamp operation.	GO to K3.

K3 CHECK FOR SHORT TO B+ IN CIRCUIT 511 (LG)

(BOO switch unplugged)
Key off.
Unplug PCM.
Key on.
Check voltage between Circuit 511 (LG) BOO connector contact and chassis ground.

Is B+ present?

Yes	No
SERVICE short to B+ in Circuit 511 (LG). REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO" and with stoplamp operation.	Short to B+ is at Pin 92 in PCM. INSPECT PCM connector and pins. SERVICE as necessary. REASSEMBLE system. GO to K11.

K4 CHECK PID "BOO"

Does PID read OFF only?

Yes	No
F-Series, GO to K5. Econoline, GO to K6.	Fault may be intermittent. GO to K13.

K5 CHECK FUSE 13 (15 AMP)

Check fuse 13 (15 amp) in IP fuse panel.

Is fuse 13 OK?

Yes	No
LOOK for open circuit. GO to K9.	THROW away fuse. LOOK for short to ground. GO to K7.

K6 CHECK FUSE 1 (15 AMP)

Check fuse 1 (15 amp) in IP fuse panel.

Is fuse 1 OK?

Yes	No
GO to K9.	THROW away fuse. LOOK for possible short to ground. GO to K7.

K7 CHECK CIRCUIT 383 (R/W) AND 10 (LG/R) FOR SHORT TO GROUND

(BOO switch unplugged)
Check resistance between circuit connector contact at BOO connector and chassis ground.

Is resistance less than 10,000 ohms?

Yes	No
SERVICE short to ground in Circuit 383 (R/W) or 10 (LG/R). REPLACE fuse 13 (15A). REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO" and with stoplamp operation.	GO to K8.

K8 CHECK CIRCUIT 511 (LG) FOR SHORT TO GROUND

(BOO switch unplugged)
Key off.
Unplug PCM.
Key on.
Check resistance between Circuit 511 (LG) contact at BOO connector and chassis ground.

Is resistance less than 10,000 ohms?

Yes	No
SERVICE short to ground in Circuit 511 (LG). REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO" and with stoplamp operation.	Short to ground is at PCM Pin 92. INSPECT PCM connector and PCM pins. SERVICE as necessary. REASSEMBLE system. GO to K12.

K9 CHECK CIRCUITS 383 (R/W) AND 10 (LG/R) FOR OPEN

(BOO switch unplugged)
(Fuse 13 unplugged).
Check resistance between circuit connector contact at BOO connector and fuse contact for Circuit 383 (R/W).

Is resistance less than 5 ohms?

Yes	No
Circuits 383 (R/W) and 10 (LG/R) are OK. GO to K10.	SERVICE open in Circuit 383 (R/W) or 10 (LG/R). REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO."

K10 CHECK BOO SWITCH FOR OPEN

(BOO switch unplugged)
Key on.
Jumper between BOO connector contacts for Circuits 511 (LG) and 10 (LG/R).
Check NGS Tester PID "BOO."

Does PID read ON?

Yes	No
REPLACE BOO switch. REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO."	GO to K11.

K11 CHECK CIRCUIT 511 (LG) FOR OPEN

(BOO switch unplugged)
Remove jumper between BOO connector contacts for Circuits 511 (LG) and 10 (LG/R).
Key off.
Unplug PCM.
Inspect 104 pin connector and repair as required.
Attach 104 pin breakout box.
Leave PCM disconnected.
Key on.
Check resistance between Test Pin 92 and BOO connector contact for Circuit 511 (LG).

Is resistance less than 5 ohms?

Yes	No
Circuit 511 (LG) is OK. Open is at PCM Pin 92. INSPECT PCM connector and pins and REPAIR as required. REASSEMBLE system. GO to K12.	SERVICE open in Circuit 511 (LG). REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO" and stoplamp operation.

K12 CONFIRM PCM FAULT

Key on, engine off.
Check NGS Tester PID "BOO."

Does PID switch between ON and OFF?

Yes	No
System is OK.	REPLACE PCM. CONFIRM fix with NGS Tester PID "BOO." RUN NGS Tester self test.

K13 CHECKS FOR INTERMITTENT OPEN OR SHORT

(BOO switch unplugged)
Key on.
Jumper between BOO connector contacts for Circuits 511 (LG) and 10 (LG/R).
Confirm that NGS Tester PID "BOO" shows ON and that stoplamps are on.
Wiggle connectors and wires while watching BOO on NGS Tester and stoplamps.

Does PID switch between ON and OFF?

Yes	No
SERVICE circuitry at point of intermittent. REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO."	GO to K14.

K14 CHECK FOR INTERMITTENT SHORT TO B+

(BOO switch unplugged)
Remove fuse.
Jumper between BOO connector contacts for Circuits 511 (LG) and 10 (LG/R).
Confirm that NGS Tester PID "BOO" shows OFF and that stoplamps are off.
Wiggle connector and wires while watching BOO on NGS Tester and stoplamps.

Does PID switch between OFF and ON?

Yes	No
SERVICE circuitry at point of intermittent contact with B+ source. INSTALL fuse. REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO." RUN NGS Tester self test.	Intermittent not detected. REASSEMBLE system. CONFIRM fix with NGS Tester PID "BOO." RUN NGS Tester self test.