2003 LEXUS LS430 Identifying ac

Fig. 68: Identifying Turbine Speed Sensor Components
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Fig. 69: DTC Reference Chart

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Reference (Using an oscilloscope):
Check the waveform between the terminals NT+ and NT- of the ECM connector.
Standard: Refer to the illustration.

Fig. 70: Identifying Waveform
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WAVEFORM REFERENCE TABLE
MONITOR DESCRIPTION
This DTC indicates that pulse is not output from the speed sensor NT (Turbine (input) speed sensor) or is output
only little. The NT terminal of the ECM detects the revolving signal from speed sensor (NT) (input RPM). The
ECM outputs a gearshift signal comparing the input speed sensor (NT) with the output speed sensor (SP2).
While the vehicle is operating in the 4th, 5th or 6th gear position in the shift position of D, if the input shaft
revolution is less than 300 rpm*1 although the output shaft revolution is more than 300 rpm or more*2, the
ECM detects the trouble, illuminates the MIL and stores the DTC.
*1: Pulse is not output or is irregularly output
*2: The vehicle speed is approx. 50 km/h (31 mph) or more.
TerminalNT+ - NT-
Tool setting1V/DIV, 2ms/DIV
Vehicle conditionEngine idle speed (P or N position)

Fig. 81: Identifying ECM Connectors
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Standard:
Fig. 82: Stop Lamp Switch Reference Chart

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NG: REPAIR OR REPLACE HARNESS OR CONNECTOR (See ELECTRONIC CIRCUIT
INSPECTION PROCEDURE )

OK: REPLACE ECM (See REPLACEMENT)
DTC P0729: GEAR 6 INCORRECT RATIO
SYSTEM DESCRIPTION
The ECM uses signals from the output speed sensor SP2 and input speed sensor NT to detect the actual gear
position (1st, 2nd, 3rd, 4th, 5th or 6th gear). Then the ECM compares the actual gear with the shift schedule in
the ECM memory to detect mechanical problems of the shift solenoid valves, valve body or automatic
transmission (clutch, brake or gear, etc.).
Fig. 83: Identifying Valve Body

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TRANSMISSION WIRE - RESISTANCE TABLE
c. Measure the resistance according to the value(s) in the table below.
Fig. 90: Identifying Transmission Wire Connector Terminals

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Standard (Check for short):
Fig. 91: Tester Connection Reference Chart

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Tester ConnectionSpecified Condition 20°C (68°F)
11 (SL1+)-3(SL1-)5.0 to 5.6 ohms

Fig. 121: Identifying Transmission Wire Connector Terminals
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Standard:
TRANSMISSION WIRE (SL2) - RESISTANCE TABLE
c. Measure the resistance according to the value(s) in the table below.
OK:
Standard (Check for short):
Tester ConnectionSpecified Condition 20°C (68°F)
10 (SL2+) - 2 (SL2-)5.0 to 5.6 ohms

OK: REPAIR OR REPLACE TRANSMISSION WIRE (See step 5 on REPLACEMENT)
DTC P0781: 1-2 SHIFT (1-2 SHIFT VALVE)
SYSTEM DESCRIPTION
The 1-2 shift valve performs shifting to 1st gear and other gears.
Fig. 126: Identifying Valve Body

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1.INSPECT TRANSMISSION WIRE (S1)
a. Disconnect the transmission wire connector from the transmission.
b. Measure the resistance according to the value(s) in the table below.
Fig. 135: Identifying Transmission Wire Terminals

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Standard:
TRANSMISSION WIRE (S1) - RESISTANCE TABLE
NG: Go to step 3
OK: Go to next step
2.CHECK HARNESS AND CONNECTOR (TRANSMISSION WIRE - ECM)
a. Connect the transmission connector to the transmission.
b. Disconnect the connector from the ECM.
Tester ConnectionSpecified Condition 20°C (68°F)
8 - Body ground11 to 15ohms