Inspection Procedure

WARNING: This page is about a different car, the 2008 Toyota Yaris. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

When replacing the tire pressure warning ECU, read the transmitter IDs stored in the old ECU using a Techstream and write them down before removal.
It is necessary to perform registration (See REGISTRATION ) of the transmitter IDs into the tire pressure warning ECU after the ECU has been replaced.

READ VALUE USING TECHSTREAM (ENGINE SPEED)

Turn the ignition switch off.
Connect a Techstream to the DLC3.
Turn the ignition switch ON and the tester ON.
Enter the following menus: Chassis / Tire Pressure Monitor / Data List

Check that the values indicated on the tester and on the combination meter are the same.

Tire Pressure Monitor

TIRE PRESSURE MONITOR DATA LIST REFERENCE

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Engine Speed	Engine speed/ min.: 0 rpm max.: 65535 rpm	Almost same as actual engine speed	Speed indicated on combination meter

OK:

Engine speed indicated on the tester and on the combination meter are the same.

NG: Go to step 2

OK: USE SIMULATION METHOD TO CHECK (See HOW TO PROCEED WITH TROUBLESHOOTING )

INSPECT TIRE PRESSURE WARNING ECU (TACH SIGNAL)

Disconnect the D78 ECU connector.

Fig 1: Inspecting Tire Pressure Warning ECU (TACH Signal)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Start the engine.

Check the waveform of the ECU connector using an oscilloscope, while idling the engine.

TESTER CONNECTION AND SPECIFIED CONDITION CHART

Tester Connection	Condition	Specified Condition
D78-4 (TACH) - D78-9 (GND)	Idling	Correct waveform is as shown

Tool Setting

TOOL SETTING

Item	Contents
Tool Setting	5V/DIV., 10 ms/DIV.

HINT:

The wavelength becomes shorter as the engine speed increases.

NG: Go to step 3

OK: REPLACE TIRE PRESSURE WARNING ECU (See TIRE PRESSURE WARNING ECU )

CHECK HARNESS AND CONNECTOR (TIRE PRESSURE WARNING ECU - ECM)

Disconnect the D78 ECU connector.

Fig 2: Identifying D78 Tire Pressure Warning ECU Connector And A21 ECM Connector

Disconnect the A21 ECM connector.

Measure the resistance according to the value (s) in the table below.

Standard resistance

RESISTANCE SPECIFICATION

Tester Connection	Condition	Specified Condition
D78-4 (TACH) - A21-15 (TACH)	Always	Below 1 Ω
D78-4 (TACH) - Body ground	Always	10 kΩ or higher

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: REPLACE ECM (See REMOVAL )