Speedometer Malfunction

METER / GAUGE / DISPLAY: METER / GAUGE SYSTEM: Speedometer Malfunction

Speedometer Malfunction

DESCRIPTION

The meter CPU receives vehicle speed signals from this circuit. The speed sensor detects the wheel speed and sends the appropriate signals to the skid control ECU. The skid control ECU supplies power to the vehicle speed sensor. The skid control ECU detects vehicle speed signals based on the pulses of the voltage. The skid control ECU transmits vehicle speed signals as pulses to the meter CPU. The meter CPU calculates the vehicle speed converting 4 pulses to 1 revolution.
HINT: Factors that affect the indicated vehicle speed include tire size, tire inflation, and tire wear. The speed indicated on the speedometer has an allowable margin of error. This can be tested using a speedometer tester (calibrated chassis dynamometer). For details about testing and the margin of error, see the reference chart On-Vehicle Inspection.

WIRING DIAGRAM

INSPECTION PROCEDURE
NOTE:
If the vehicle speed is outside the allowable range when tested, perform the following procedure On-Vehicle Inspection.
HINT: Before starting circuit inspection, check tire size and tire pressure.

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (SPEED METER OPERATION)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Body Electrical / Combination Meter / Active Test.
(e) Check the operation by referring to the table below.

Combination Meter

- *1: for U.S.A.
- *2: for Canada

OK:
Speedometer indication is normal.
NG -- REPLACE COMBINATION METER
OK -- Continue to next step.

2. READ VALUE USING TECHSTREAM (VEHICLE SPEED METER)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Body Electrical / Combination Meter / Data List.
(e) Check the values by referring to the values in the table below.

Combination Meter

OK:
Vehicle speed displayed on the Techstream is almost the same as the actual vehicle speed measured using a speedometer tester (calibrated chassis dynamometer).
NG -- READ VALUE USING TECHSTREAM (FL/FR/RL/RR WHEEL SPEED)
OK -- REPLACE COMBINATION METER
3. READ VALUE USING TECHSTREAM (FL/FR/RL/RR WHEEL SPEED)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.
(e) Check the values by referring to the table below.

ABS/VSC/TRAC

(a) Disconnect the J77 connector.
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:

NG -- CHECK HARNESS AND CONNECTOR (COMBINATION METER - SKID CONTROL ECU)
OK -- Continue to next step.

5. INSPECT SKID CONTROL ECU (INPUT WAVEFORM)

(a) Check the input signal waveform.
(1) Remove the combination meter with connector(s) still connected.
(2) Reconnect the J77 connector.
(3) Connect the oscilloscope to the terminals J34-17 (SI) and body ground.
(4) Turn the engine switch on (IG).
(5) Turn the drive wheel slowly.
(6) Check the signal waveform according to the condition(s) in the table below.

OK:
The waveform is displayed as shown in the illustration.
HINT: When the system is functioning normally, one drive wheel revolution generates 4 pulses. As the vehicle speed increases, the width indicated by (A) in the illustration narrows.

NG -- REPLACE SKID CONTROL ECU
OK -- REPLACE COMBINATION METER
6. CHECK HARNESS AND CONNECTOR (COMBINATION METER - SKID CONTROL ECU)

(a) Disconnect the J34 and J77 connectors.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE COMBINATION METER