1996 Bronco/F-Series

Section 06-09B: Brake, Anti-Lock, 4-Wheel

1996 Bronco Workshop Manual

DIAGNOSIS AND TESTING

System Precheck

NOTE: It is imperative that this procedure be performed first. Failure to do so may result in incorrect diagnosis of problem, wasted time and improper replacement of good components.

NOTE: Perform the following measurements with Rotunda 88 Digital Multimeter 105-00053 or equivalent. If not using a Rotunda 105-00053 or Fluke Frequency Meter, higher wheel speeds may be required in order for the frequency meter to function correctly.

The system precheck is used to screen a vehicle for relatively simple diagnostic repairs such as loose connectors, blown fuses, etc. However, the system precheck is also used to prepare the vehicle for further diagnostics. In addition, warning lamp faults are dealt with in this test.

Precheck

PC1 PERFORM UNDERHOOD SYSTEM PRECHECK

Verify that all of the following connectors are connected and the terminals are secure and free of contaminants or corrosion.

40-pin anti-lock brake electronic control module connector
8-pin anti-lock hydraulic control unit connector
4-pin pump motor connector
2-pin front brake anti-lock sensor connectors (2)

Open power distribution box and the trailer relay box and verify that the system relay, pump motor relay and system diode are fully seated.
Gently pull on relay and diode terminals from beneath to make sure all are secure.
Verify that both the system fuse and pump motor fuse are present and intact.
Verify that the system ground eyelet at the left-hand radiator support is firmly attached to the weld stud and is free of corrosion and excessive dirt.

Are all connections secure and fuses operational?

Yes	No
GO to PC2.	CORRECT condition. GO to PC2.

PC2 PERFORM UNDER-VEHICLE SYSTEM PRECHECK

Verify that the 3-pin acceleration sensor connector and the 2-pin vehicle speed sensor connector at the rear axle are connected and the terminals are secure and free of contaminants or corrosion.

Are all connectors, terminals and grounds secure?

Yes	No
GO to PC3.	SERVICE as required. GO to PC3.

PC3 CHECK ABS WARNING LIGHT SEQUENCE (KEY ON/ENGINE OFF)

Parking brake released.
Observe ABS warning light on dash.
Key to RUN.

Does ABS warning light come on?

Yes	No
If light flashes, diagnostic circuit is grounded. CORRECT condition. If light stays on for 3 seconds and goes out (normal bulb prove out), GO to PC6. If light comes on and stays on (hard light), GO to PC4.	GO to PC7.

Yes

If light flashes, diagnostic circuit is grounded. CORRECT condition.

If light stays on for 3 seconds and goes out (normal bulb prove out), GO to PC6.

If light comes on and stays on (hard light), GO to PC4.

GO to PC7.

PC4 CODE RETRIEVAL EQUIPMENT HOOKUP

Verify that an ABS concern has been detected (ABS warning light on).
Key off.
If using Rotunda New Generation Star Tester 007-00500 or equivalent:

Connect tester to red ABS data link connector.
Turn test power on and put HOLD/TEST button in TEST position.

If using 12V test light or ABS warning light:

Locate red ABS data link connector and install 12V test light between Circuit 603 (DG) and Circuit 57 (BK).
If no test light is available, ABS warning light will flash.

Jumper ABS data link connector terminals for Circuit 606 (BK/LB) and Circuit 57 (BK).

Is equipment hooked up properly?

Yes	No
GO to PC5.	REATTEMPT PC4. SERVICE as required.

PC5 RETRIEVE ABS DIAGNOSTIC TROUBLE CODES

If using Rotunda New Generation Star Tester 007-00500 or equivalent:

Key to RUN.
Read out and record all diagnostic trouble codes.

CAUTION: Be sure to read out and record all codes. Failure to do so may result in improper diagnosis and unnecessary repairs.

If using 12V test light or ABS warning light:

Key to RUN.
Count flashes.

NOTE: Digits will be separated by 3-6 seconds. Diagnostic trouble codes will be separated by 15 seconds.

Record all codes. When flashing stops, there are no codes remaining.
Remove jumper in ABS TEST connector.

Are there any codes present?

Yes	No
If anything other than Code 16, and starting with the first code recorded, GO to the pinpoint test for that code. If Code 16, and if previous action has been taken, concern most likely has been corrected and ABS system is OK. Otherwise, GO to PC6.	GO to Pinpoint Test V.

Yes

If anything other than Code 16, and starting with the first code recorded, GO to the pinpoint test for that code.

If Code 16, and if previous action has been taken, concern most likely has been corrected and ABS system is OK. Otherwise, GO to PC6.

GO to Pinpoint Test V.

PC6 ROAD TEST VEHICLE

NOTE: This step is optional, for additional information only.

Drive vehicle under the following conditions and observe ABS warning light.

When vehicle moves initially (light comes on at or near 6 mph).
While driving under 25 mph.
While driving at or over 25 mph.
While in an anti-lock stop.

Does ABS warning light come on during any of the above conditions?

Yes	No
At or near 6 mph, concern most likely found during pump check. GO to PC4. VERIFY pump diagnostic trouble code has been set. While driving under 25 mph, most likely cause is missing sensor output. GO to PC4. VERIFY sensor diagnostic trouble code has been set. While driving over 25 mph, most likely cause is an erratic sensor output. GO to PC4. VERIFY sensor diagnostic trouble code has been set.	Vehicle has abnormal ABS or brake system operation. GO to Symptom Chart. No abnormal operation or symptoms detected. GO to PC4. VERIFY Code 16 (System OK) is present.

Yes

At or near 6 mph, concern most likely found during pump check. GO to PC4. VERIFY pump diagnostic trouble code has been set.

While driving under 25 mph, most likely cause is missing sensor output. GO to PC4. VERIFY sensor diagnostic trouble code has been set.

While driving over 25 mph, most likely cause is an erratic sensor output. GO to PC4. VERIFY sensor diagnostic trouble code has been set.

Vehicle has abnormal ABS or brake system operation. GO to Symptom Chart.

No abnormal operation or symptoms detected. GO to PC4. VERIFY Code 16 (System OK) is present.

PC7 ABS WARNING LIGHT DOES NOT PROVE OUT/CHECK BULB

Inspect ABS warning light bulb in dash.

Is the bulb blown?

Yes	No
REPLACE bulb. GO to PC3.	LEAVE bulb out. GO to PC8.

PC8 VERIFY ABS WARNING LAMP FEED IS INTACT

Key off.
Insert 12V test light between ABS bulb socket (+) and a known good chassis ground.
Key on.

Does test light illuminate?

Yes	No
GO to PC9.	SERVICE open circuit or short to ground on warning light feed. REINSERT bulb into socket. GO to PC3.

PC9 VERIFY ABS WARNING LAMP GROUND BETWEEN BULB AND SYSTEM DIODE

Open relay box and remove system diode.
Verify diode terminals are clean and firmly in place.
Check for continuity between ABS bulb socket ground and diode terminal in trailer relay box for Circuit 603 (DG).

Is there continuity?

Yes	No
GO to PC10.	SERVICE open circuit in warning light ground or loose terminal. REINSERT ABS diode. GO to PC3.

PC10 VERIFY INTACT ABS WARNING LAMP GROUND BETWEEN ABS DIODE AND ABS MAIN RELAY

Remove ABS main relay.
Verify relay terminals are clean and firmly in place.
Check for continuity between ABS diode Circuit 532 (O/Y) and ABS main relay Circuit 532 (O/Y).

Is there continuity?

Yes	No
GO to PC11.	SERVICE open circuit in Circuit 532 (O/Y) between ABS diode and ABS main relay or loose terminals. REINSERT ABS diode and main relay. GO to PC3.

PC11 CHECK GROUND BETWEEN ABS MAIN RELAY AND CHASSIS GROUND

Inspect chassis ground stud at left-hand radiator support for loose or corroded eyelets.
Clean and tighten any loose or dirty ground eyelets.
Check for continuity between ABS main relay Circuit 57 (BK) and left-hand radiator support chassis ground stud.

Is there continuity?

Yes	No
REINSERT ABS main relay. REPLACE ABS warning bulb. REPEAT Steps PC8-PC11 looking for intermittent condition. REFER to Pinpoint Tes (Intermittent Diagnosis).	SERVICE open circuit between ABS main relay and chassis ground. REINSERT ABS main relay. GO to PC3.