Toyota Pick-ups/Land Cruiser/4Runner 1989-1996

Diagnosis and Testing



Certain components within the system are not intended to be serviced or repaired individually. Only those components with removal and installation procedures should be serviced.
Do not use rubber hoses or other parts not specifically specified for the anti-lock system. When using repair kits, replace all parts included in the kit.
Use only DOT 3 brake fluid from an unopened container.
If any hydraulic component (either power steering or brake) is removed or replaced, it may be necessary to bleed the entire system.
A clean repair area is essential. Always clean the reservoir and cap thoroughly before removing the cap. The slightest amount of dirt in the fluid may plug an orifice and impair the system function. Perform repairs after components have been thoroughly cleaned; use only denatured alcohol to clean components. Do not allow components to come into contact with any substance containing mineral oil; this includes used shop rags.
The ECU is a microprocessor similar to other computer units in the vehicle. Insure that the ignition switch is OFF before removing or installing controller harnesses. Avoid static electricity discharge at or near the controller.
If any arc welding is to be done on the vehicle, the ECU should be disconnected before welding operations begin.
If the vehicle is to be baked after paint repairs, remove the ECU from the vehicle.


If a malfunction occurs, the system will identify the problem and the computer will assign and store a fault code for the fault(s). The dashboard warning lamp will be illuminated to inform the driver that a fault has been found.

During diagnostics, the system will transmit the stored code(s) by flashing the dashboard warning lamp. If two or more codes are stored, they will be displayed from lowest number to highest, regardless of the order of occurrence. The system does not display the diagnostic codes while the vehicle is running.

Visual Inspection

Before diagnosing an apparent rear anti-lock problem, make absolutely certain that the normal braking system and power steering systems are in correct working order. Many common problems (dragging parking brake, seepage, etc.) will affect the ABS system. A visual check of specific system components may reveal problems creating an apparent ABS malfunction. Performing this inspection may reveal a simple failure, thus eliminating extended diagnostic time.

Inspect the brake fluid level in the reservoir.
Inspect lines, hoses, master cylinder assembly, brake calipers and cylinders for leakage. Inspect the power steering system and components for the same conditions.
Visually check lines and hoses for excessive wear, heat damage, punctures, contact with other parts, missing clips or holders, blockage or crimping.
Check the calipers or wheel cylinders for rust or corrosion. Check for proper sliding action if applicable.
Check the caliper and wheel cylinder pistons for freedom of motion during application and release.
Inspect the speed sensor for proper mounting and correct connection.
Confirm the fault occurrence. Certain driver induced faults, such as not releasing the parking brake fully, will set a fault code and trigger the dash warning light. Excessive wheel spin on low-traction surfaces, high speed acceleration or riding the brake pedal may also set fault codes and trigger a warning lamp. These induced faults are not system failures but examples of vehicle performance outside the parameters of the control unit.
Many system shut-downs are due to loss of sensor signals to or from the controller. The most common cause is not a failed sensor but a loose, corroded or dirty connector. Check harness and component connectors carefully.

Reading Codes

See Figure 1

  1. Turn the ignition switch OFF . Check battery condition; approximately 12 volts is required to operate the system.
  3. Turn the ignition switch ON and check that the ABS dashboard warning lamp comes on for 3 seconds. If the lamp does not come on, repair the fuse, bulb or wiring.

Click image to see an enlarged view

Fig. Fig. 1: Diagnostic trouble codes for 4-wheel ABS

  1. Use a jumper wire to attach terminals Tc and E1 of the Data Link Connector (DLC1). This is not the service connector. Turn the ignition ON .
  3. If a fault code has been set, the dashboard warning lamp will begin to blink 4 seconds later. The number of flashes corresponds to the first digit of a 2-digit code; after a 1.5 second pause, the second digit is transmitted. If a second code is stored, it will be displayed after a 2.5 second pause. Once all codes have been displayed, the entire series will repeat after a 4 second pause. If no codes have been stored, the warning lamp will flash continuously every 1 / 2 second with no variation.
  5. Turn the ignition switch OFF .
  7. Check or repair the system as indicated by the fault code.
  9. After repairs are completed, clear the codes from the memory. If the battery is disconnected during repairs, the controller memory will be erased of all stored codes.
  11. Remove the jumper wire if one was used and reattach the service connector at the actuator.

Clearing Codes
  1. Detach the service connector at the actuator.
  3. Use the jumper wire to connect terminals Tc and E1 of the Data Link Connector (DLC1). Turn the ignition ON .
  5. Clear the diagnostic trouble codes stored in the ECU by depressing the brake pedal 8 or more times within 3 seconds.
  7. After the rapid pedal application, the dash warning lamp should display constant flashing, indicating a normal system. If codes are still displayed, make certain the repairs made to the system are correct. Also inspect the brake light switch at the brake pedal for any binding or sticking.
  9. Once the codes are cleared, disconnect the jumper wire. The dash warning lamp should go out.