Traction Control System: Diagnosis Lexus LS II

SELF-DIAGNOSTIC SYSTEM

Note. DO NOT start engine when accessing diagnostic codes.

RETRIEVING DIAGNOSTIC TROUBLE CODES

1. Turn ignition switch to ON position. Ensure TRAC OFF (except GS300) or TRAC (GS300) indicator light illuminates for 3 seconds and turns off. If TRAC OFF (except GS300) or TRAC (GS300) indicator light does not function as indicated see TRAC OFF INDICATOR, TRAC CUT SWITCH CIRCUIT test.
2. On all models except GS300, ensure ignition switch is in ON position. If a DTC is set, after TRAC OFF indicator light has illuminated for 3 seconds, it will begin blinking every 1.5 seconds. If DTC 53 is set TRAC OFF indicator may remain on (without blinking) until engine is started.
3. On all vehicles, ensure ignition switch is in ON position. Using a fused jumper wire or service connector (SST 09843-18020), connect terminals Tc and E1 of Data Link Connector No. 1 (DLC1) or Data Link Connector No. 2 (DLC2). (Scheme 33) DLC1 is located in engine compartment, left front side of plenum chamber, across from strut tower. DLC2 is located under left side of instrument panel (GS300) or right side of instrument panel (SC300 and SC400), near kick panel. On LS400 DLC2 is located under center of instrument panel.
4. On all models, turn ignition on. If a malfunction is detected, TRAC OFF indicator light will begin to flash a 2-digit DTC after 4 seconds. TRAC OFF indicator light will flash first digit, followed by a 1.5-second pause and then second digit.
5. Count number of flashes to obtain digits of 2-digit code. If 2 or more codes are stored, a 2.5-second pause will separate codes. If 2 or more malfunctions are indicated at the same time lowest numbered DTC will be displayed first. See DIAGNOSTIC TROUBLE CODE IDENTIFICATION table for code diagnosis SELF-DIAGNOSTICS.
6. If ABS is functioning properly a normal code will be set. During normal code, 2 seconds will elapse, and then TRAC OFF indicator light will blink once every.25 second.
7. If TRAC OFF (except GS300) or TRAC (GS300) indicator light does not illuminate, see Tc TERMINAL CIRCUIT or TRAC INDICATOR LIGHT CIRCUIT tests. After replacing or repairing malfunctioning components, clear diagnostic trouble codes, see «CLEARING DIAGNOSTIC TROUBLE CODES (DTCS)»(ref-124943-S34206223592001100400000). Turn ignition off. Remove fused jumper wire or service connector (SST 09843-18020), from DLC1 or DLC2 connector.

Scheme 33

IDENTIFYING DIAGNOSTIC TROUBLE CODES (1997)

IDENTIFYING DIAGNOSTIC TROUBLE CODES (1998)

CLEARING DIAGNOSTIC TROUBLE CODES (DTCS)

Note. On GS300, DTCs can also be cleared by removing ECU-B (7.5-amp) fuse. Removing ECU-B (7.5-amp) fuse will also erase other memory systems. ECU-B (7.5-amp) fuse is located in relay block at left side of engine compartment.

Turn ignition on. Using a jumper wire or service connector (SST 09843-18020), connect DLC1 or DLC2 terminals Tc and E1. (Scheme 33) With vehicle stopped, depress brake pedal 8 or more times within 3 (GS300) or 5 (except GS300) seconds. Ensure TRAC OFF (except GS300) or TRAC (GS300) indicator light turns on. Remove jumper wire or service connector (SST 09843-18020).

Circuit Description

SLIP indicator blinks during TRAC operation. TRAC indicator is used for displaying DTC and indicating trouble.

Diagnosis & Repair

Inspect TRAC indicator light. Replace as needed. If light is okay, check for short in wire harness circuit between TRAC ECU and TRAC indicator light. Repair as necessary. If circuit is okay, replace TRAC ECU.

Turn ignition on. Check voltage between terminals Tc and E1 of DLC1 or DLC2. (Scheme 33) If 10-14 volts (LS400) or 8-14 volts (except LS400) is present, circuit is okay (ABS/TRAC ECU may be faulty if light does not blink when connecting a jumper wire between terminals Tc and E1). If 10-14 volts (LS400) or 8-14 volts (except LS400) is not present, check circuits between ABS/TRAC ECU, DLC1 and DLC2, and ground. If circuits are okay, replace ABS/TRAC ECU.

TRAC indicator blinks during TRAC operation. TRAC indicator is used for displaying DTC and indicating trouble.

1. Determine if any DTCs are present. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-124943-S42410388882001100400000) under SELF-DIAGNOSTIC SYSTEM. Repair as needed. If no DTCs exist, go to next step.
2. Inspect TRAC indicator light. Replace as needed. If light is okay, check for short in wire harness circuit between TRAC ECU and TRAC indicator light. Repair as necessary. If circuit is okay, replace TRAC ECU.

When TRAC cut switch is pushed on, TRAC control goes off and TRAC OFF indicator illuminates. TRAC OFF indicator blinks when malfunction occurs and for displaying DTCs (except GS300).

1. Determine if any ABS DTCs are present. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-124943-S42410388882001100400000) under SELF-DIAGNOSTIC SYSTEM. Repair as needed. If no DTCs exist, go to next step.
2. Remove TRAC cut switch. Disconnect harness connector. Check continuity between terminals No. 2 and 3 (LS400), No. 2 and 6 (SC300, SC400) or No. 1 and 2 (GS300) on switch connector. (Scheme 34)or see scheme 20. Continuity should only exist when switch button is pressed. Replace switch as needed. If switch is okay, go to next step.
3. Check continuity of CSW circuit between TRAC cut switch and ABS/TRAC ECU. Repair as needed. If circuit is okay, go to next step.
4. Inspect TRAC OFF indicator light. Replace as needed. If light is okay, go to next step.
5. Check continuity of WT circuit between TRAC OFF indicator light and ABS/TRAC ECU. Repair as needed. If circuit is okay, replace ABS/TRAC ECU.

Scheme 34

Scheme 35

DTC 24: TRAC SUB-THROTTLE ACTUATOR CIRCUIT (1997)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

On all models except LS400, sub-throttle actuator operates in accordance with signals from ECU. ECU controls opening and closing of sub-throttle valve. On LS400, sub-throttle actuator operates in accordance with signals from throttle valve motor driver. Throttle valve motor driver controls opening and closing of sub-throttle valve. DTC is set when ECU detects open or short in sub-throttle actuator circuit. Possible causes are

1. TRAC fuse.
2. BM open or short circuit.
3. Sub-throttle actuator.
4. Sub-throttle actuator open or short circuit.
5. Throttle valve motor driver.

1. Remove TRAC fuse from instrument panel junction or relay block. On LS400, junction block is located behind parking brake release lever. On all except LS400, relay block is located at left side of engine compartment. Inspect fuse. If fuse is okay, go to next step. If fuse is blown, inspect and repair circuit between fuse and throttle valve motor driver (except GS300) or TRAC ECU (GS300). Replace fuse.
2. Using voltmeter, backprobe throttle valve motor driver connector (except GS300) or TRAC ECU (GS300). On all models except GS300, measure voltage between terminals No. 1 (Blue/Red wire) and 12 (White/Black wire) on connector T6 (LS400) or T12 (SC300 and SC400). If voltage is 10-14 volts, go to next step.
3. If voltage is not 10-14 volts, check for open or short in Blue/Red wire between TRAC fuse and throttle valve motor driver. Also check for open in White/Black wire between throttle valve motor driver and ground terminal. On LS400, ground terminal is located at right instrument panel brace, and ground terminal located at right side of instrument panel. On SC300 and SC400, ground terminal is located at right kick panel.
4. On GS300, measure voltage between terminal No. 15 (Blue/Red wire) and ground on connector T13. If voltage is 10-14 volts, go to next step. If voltage is not 10-14 volts, check for open or short in Blue/Red wire between TRAC fuse and TRAC ECU.
5. Disconnect sub-throttle actuator connector. Actuator is mounted to throttle body. Using ohmmeter, measure resistance between sub-throttle actuator component terminals. See «SUB-THROTTLE ACTUATOR CONTINUITY»(ref-124943-S15782498452001100400000) table. If .9 ohms (except GS300) or .8-1 ohms (GS300) of resistance exists in all circuits, go to next step. If .9 ohms (except GS300) or .8-1 ohms (GS300) or resistance does not exist, replace actuator. SUB-THROTTLE ACTUATOR CONTINUITY Terminals Continuity 1 & 2 Yes 2 & 3 Yes 4 & 5 Yes 5 & 6 Yes
6. Ensure ignition is off. Disconnect throttle valve motor driver (except GS300) or TRAC ECU (GS300) connectors. Using ohmmeter, check for open or short (except LS400, short on LS400) in wire harness circuits between throttle valve motor driver (except GS300) or TRAC ECU (GS300) and sub-throttle actuator. Repair circuit(s) as needed. On LS400, if circuits are okay, go to next step. On SC300 and SC400, if circuits are okay, replace throttle valve motor driver. On GS300, if circuits are okay, replace TRAC ECU.
7. On LS400, disconnect ABS/TRAC ECU. Check for open or short in wire harness circuits between throttle valve motor driver and ABS/TRAC ECU. Repair circuit(s) as needed. If continuity are okay, replace throttle valve motor driver.

DTC 25 OR 26: TRAC SUB-THROTTLE VALVE

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

DTC 25 is set when, sub-throttle sensor signal voltage is 1 volt (GS300) or 1.8 volts (except GS300) or greater than required step count. DTC 26 is set when, sub-throttle valve is commanded to full open position, input voltage at VSH (GS300) or VTA2 (except GS300) circuit on ECM is not 3-4.5 volts. Possible causes are

1. Sub-throttle actuator.
2. Throttle body (faulty valve).
3. Sub-throttle position sensor.
4. Sub-throttle position sensor open or short circuit.
5. Engine Control Module (ECM).
6. Throttle Valve Motor Driver (Except GS300).
7. TRAC ECU (Except GS300).

Remove air cleaner duct to throttle body. Manually open and close sub-throttle valve and ensure valve operates smoothly. Possible causes of valve not operate smoothly are

1. Sub-throttle actuator.
2. Sub-throttle valve.
3. Sub-throttle position sensor.
4. Sub-throttle position sensor open or short circuit.
5. Engine Control Module (ECM). If ECM is okay, replace throttle valve motor driver (except GS300) or TRAC ECU (GS300).

DTC 28 OR 29: THROTTLE VALVE MOTOR DRIVER (1997, EXCEPT GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

Two circuits (TRC+, TRC-) are used to send TRAC control information from the ABS/TRAC ECU to the throttle valve motor driver. The THD circuit sends response information from the throttle valve motor driver to the ABS/TRAC ECU. DTC 28 is set when no THD data is received from throttle valve motor driver, or a signal is received from throttle motor driver indicating a malfunction in TRC+ or TRC- circuit(s) for 5 seconds. DTC 29 is set when a signal is received by ABS/TRAC ECU that sub-throttle actuator is being commanded during TRAC non-operation or a signal is received by ABS/TRAC ECU that sub-throttle actuator is being driven during TRAC operation (but not currently being commanded). Possible causes are

1. THD open or short circuit.
2. TRC+ open or short circuit.
3. TRC- open or short circuit.
4. Throttle valve motor driver.
5. ABS/TRAC ECU.

Ensure ignition is off. Disconnect throttle valve motor driver harness connectors and ABS/TRAC ECU harness connectors. Using ohmmeter, check for open or short in Red, White or Black wires (LS400), or Blue, Black/White or Pink wires (1997 SC300 and SC400) between ABS/TRAC ECU and throttle valve motor driver. Repair as needed. If all circuits are okay, replace throttle valve motor driver or ABS/TRAC ECU, or both.

DTC 31, 32, 33 OR 34: SPEED SENSOR CIRCUIT (GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

Speed sensor at each wheel produces an A/C signal and sends it to ABS/TRAC ECU as 48-tooth rotor passes a permanent magnet sensor. Frequency of A/C signal changes with wheel speed. DTCs are set under the following conditions

1. No speed sensor pulses are input to ECU for 5 seconds with vehicle speed 6 MPH or greater.
2. Momentary interruption of speed sensor signal occurs at least 7 times during cycle of ignition switch.
3. Abnormal speed sensor signal fluctuation with vehicle speed of 12 MPH or greater.

If trouble occurs in speed sensor circuit, ECU performs a fail safe function, turning off current and prohibiting TRAC control. Possible causes are

1. Speed sensor.
2. Speed sensor open or short circuit.
3. Open or short in FRO, FLO, RRO or RLO circuit.
4. Speed sensor rotor.

1. Check ABS warning light. If ABS warning light flashes same number DTC. Diagnose ABS system before preceding with this test. See appropriate ANTI-LOCK BRAKE article. If ABS system DTC is okay, go to next step.
2. Disconnect ABS/TRAC ECU T13 connector and TRAC ECU T14 connector. Check for open or short in Green, Green/Yellow, Green/Red and Green/Black wires between ABS/TRAC ECU T13 connector and TRAC ECU T14 connector. Repair wires as necessary. If wires are okay, go to next step.
3. Ensure ignition switch is in LOCK position. On front speed sensors, remove fender liner. Disconnect front speed sensor connector. Measure resistance between sensor component terminals. If resistance is 600-2500 ohms, go to next step. If resistance is not 600-2500 ohms, replace speed sensor. Verify speed sensor signal. See SPEED SENSOR SIGNAL CHECK. See appropriate ANTI-LOCK BRAKE article.
4. Check for continuity between front speed sensor terminals and ground. If continuity exists, replace speed sensor. If continuity does not exist, go to next step. Verify speed sensor signal. See SPEED SENSOR SIGNAL CHECK. See appropriate ANTI-LOCK BRAKE article.
5. On rear speed sensors, remove rear seat cushion, seat back and quarter trim. Disconnect rear speed sensor connector. Measure resistance between sensor component terminals. If resistance is 650-1800 ohms, go to next step. If resistance is not 650-1800 ohms, replace speed sensor. Verify speed sensor signal. See SPEED SENSOR SIGNAL CHECK. See appropriate ANTI-LOCK BRAKE article.
6. Check for continuity between rear speed sensor terminals and ground. If continuity does not exist, go to next step. If continuity exists, replace speed sensor. Verify speed sensor signal. See SPEED SENSOR SIGNAL CHECK. See appropriate ANTI-LOCK BRAKE article.
7. Inspect each circuit between speed sensor and ABS/TRAC ECU for short or open. See «WIRING DIAGRAMS»(ref-124943-S17075049372001100400000) . Repair as needed. If circuits are okay, go to next step.
8. For DTC 31 or 32, remove appropriate front axle shafts. See appropriate FWD AXLE SHAFTS article in DRIVE AXLES. Inspect speed sensor rotor for damage. Replace as necessary. Remove appropriate front speed sensor. See SPEED SENSOR under «REMOVAL & INSTALLATION»(ref-124943-S24165020902001100400000) . Check speed sensor tip for damage. Replace as necessary. Verify speed sensor signal. See SPEED SENSOR SIGNAL CHECK. If speed sensor rotor and speed sensor are okay, replace ABS ECU.
9. For DTC 33 or 34, remove appropriate rear hub assembly. See REAR SUSPENSION article in SUSPENSION. Inspect speed sensor rotor for damage. Replace as necessary. Remove appropriate rear speed sensor. See SPEED SENSOR under «REMOVAL & INSTALLATION»(ref-124943-S24165020902001100400000) . Check speed sensor tip for damage. Replace as necessary. Verify speed sensor signal. See SPEED SENSOR SIGNAL CHECK. See appropriate ANTI-LOCK BRAKE article. If speed sensor rotor and speed sensor are okay, replace ABS ECU.

DTC 41: IG POWER SUPPLY CIRCUIT

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

Voltage is supplied from ignition switch to ABS/TRAC ECU and actuators. DTC is set when ECU detects voltage of 17 volts or greater for more than 5 seconds. DTC is also set when ECU detects voltage of 9.5 volts or greater for more than 10 seconds, with engine speed or 500 RPM or greater. If trouble occurs in power source circuit, ECU performs a fail safe function, turning off current and prohibiting TRAC control. Possible causes are

1. Battery.
2. Regulator.
3. Power supply open or short circuit.

1. Ensure battery voltage is 10-14 volts. Gain access to ABS/TRAC ECU. Do not disconnect harness connectors. Measure resistance or voltage by backprobing connector.
2. Turn ignition on. Measure voltage between terminals No. 2 (Black/Red wire) and 14 (Black/White wire) on TRAC ECU connector T13. If voltage is not 10-14 volts, go to next step. If voltage is 10-14 volts, turn ignition off and replace ABS/TRAC ECU.
3. Measure resistance between ground and terminal No. 14 (Black/White wire) on TRAC ECU connector T13. If resistance is less than one ohm, go to next step. If resistance is one ohm or greater, check for open between terminal No. 14 on TRAC ECU connector T13 and ground terminal located at right kick panel.
4. Inspect ECU-IG (10-amp) fuse in instrument panel junction block. Instrument panel junction block is located at left kick panel. If fuse is blown, inspect circuit between battery and TRAC ECU for short. If fuse is not blown, inspect circuit between battery and TRAC ECU for open. Repair as needed.

DTC 43: ABS CONTROL SYSTEM MALFUNCTION (EXCEPT GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

DTC is set when ABS control system is malfunctioning. Possible cause is ABS control system.

Determine if ABS DTCs are present. See appropriate ANTI-LOCK BRAKE article. Repair ABS system as needed. If no DTCs are present, inspect circuit between ABS/TRAC ECU and malfunction indicator light.

DTC 43: ABS/TRAC CONTROL SYSTEM MALFUNCTION (GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

DTC is set when ABS or TRAC control system or communication circuit is malfunctioning. Possible causes are

1. BRFA circuit is open or short.
2. ABS/TRAC control system.

Note. Clear DTC after completing repairs. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS).

1. Determine if ABS DTCs are present. See appropriate ANTI-LOCK BRAKE article. Repair ABS system as needed. If no DTCs are present, go to next step.
2. Access TRAC ECU. Do not disconnect connectors. Turn ignition on. Backprobing, measure voltage between ground and terminal No. 4 (Light Green wire) on TRAC ECU T14 connector. If voltage is a 6 volt pulse, replace TRAC ECU. If voltage is not a 6 volt pulse, go to next step. NOTE: Voltage must be measured within 8 seconds of disconnecting TRAC ECU harness connector.
3. Turn ignition off. Disconnect TRAC ECU T14 connector. Turn ignition on. Measure voltage between ground and terminal No. 4 (Light Green wire) on TRAC ECU T14 connector. If voltage is a 6-volt pulse, replace TRAC ECU. If voltage is not a 6-volt pulse, go to next step.
4. Turn ignition off. Check for open or short in Light Green wire between ABS/TRAC ECU and TRAC ECU. Repair circuit as needed. If circuit is okay, replace TRAC ECU.

DTC 44: NE SIGNAL CIRCUIT MALFUNCTION

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

ABS/TRAC ECU (except GS300) or TRAC ECU (GS300) receives engine speed signals from Engine Control Module (ECM) on NE circuit. DTC is set when there is no NE signal input to ECM after traction control is initiated for .24 seconds. Possible causes are

1. Open or short in NEO circuit.
2. ECM.
3. ABS/TRAC ECU.

1. Turn ignition off. Check for open or short in Violet/Red wire (LS400), Brown/White wire (GS300), or Pink/Blue wire (SC300 and SC400) between ECM and ABS ECU. Repair circuit as needed. If circuit is okay, go to next step.
2. Turn ignition on. Backprobing, measure voltage between ground and ABS/TRAC ECU T7 connector terminal No. 15 (Violet/Red wire -LS400), TRAC ECU T13 connector terminal No. 6 (Brown/White wire - GS300), ABS/TRAC ECU T13 connector terminal No. 15 (Pink/Blue wire - 1997 SC300 and SC400), or ABS/TRAC ECU A21 connector terminal No. 15 (Pink/Blue wire - 1998 SC300 and SC400).
3. With ignition switch in ON position 3-6 volts or less than one volt should exist. Turn engine on and allow to idle. With engine idling 2-3 volt pulse should exist. If voltage is as specified, go to next step. If voltage is not at specified, replace ABS/TRAC ECU (except GS300) or TRAC ECU (GS300).
4. Clear codes. See «CLEARING DIAGNOSTIC TROUBLE CODES (DTCS)»(ref-124943-S34206223592001100400000) under SELF-DIAGNOSTIC SYSTEM. Retrieve DTCs. If DTC 44 is still present, check condition of connectors. Repair as needed.

DTC 45 OR 46: MAIN THROTTLE POSITION SENSOR CIRCUIT (GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

Main Throttle Position (TP) sensor circuits indirectly affect TRAC control system when a malfunction occurs. TRAC system may be switched off as a fail safe function. DTC 45 is set when IDL switch of main TP sensor is on or input voltage to VTH circuit of TRAC ECU is 1.45 volts or greater. DTC 46 is set when VTH circuit of TRAC ECU is 4.9 volts or greater, or VTH circuit of TRAC ECU is .2 volts or greater when IDL1 circuit is off. Main TP sensor signal is transmitted to TRAC ECU from Engine Control Module (ECM). If a problem occurs at engine both ECM and TRAC ECU will detect it. Possible causes are

1. Main TP sensor.
2. VTH open circuit.
3. IDL1 short circuit.

Note. Clear DTC after completing repairs. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS).

1. Determine if any engine DTCs are present. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE section. Repair as needed. If no engine DTCs exist, go to next step.
2. Access TRAC ECU. Do not disconnect connectors. Remove air intake duct at throttle body. Turn ignition on. Backprobing TRAC ECU connector T13, measure voltage between ground and terminal No. 8 (Pink/Blue wire). Monitor voltage while opening main throttle valve to wide open throttle. Voltage should be 1.5 volts or less with throttle fully closed, and 3-4.5 volts with throttle fully open. If voltage is within specification, go to step 7). If voltage is not within specification, go to next step.
3. Turn ignition off. Check open or short in Pink/Blue wire between TRAC ECU connector T13 and ECM. Repair as needed. If circuit is okay, go to next step.
4. Install ECM test harness. Disconnect TRAC ECU harness connectors. Turn ignition on. Measure voltage between ground and terminal No. 40 on test connector "A". Monitor voltage while opening main throttle valve to wide open throttle. Voltage should be 1.5 volt or less with throttle fully closed, and 3-4.5 volts with throttle fully open. If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
5. Measure voltage between terminals No. 43 and 65 on test connector "B". Monitor voltage while opening main throttle valve to wide open throttle. Voltage should be .3-.8 volts with throttle fully closed, and 3.2-4.9 volts with throttle fully open. If voltage is within specification, replace ECM. If voltage is not within specification, go to next step.
6. Turn ignition off. Check continuity of VTA1 circuit between main TP sensor and ECM. Repair as needed. Ensure circuit is not shorted to ground. If circuit is okay, adjust or replace main TP sensor. See appropriate SYSTEM & COMPONENT TESTING article in ENGINE PERFORMANCE section.
7. Turn ignition on. Backprobing TRAC ECU harness connector T13, measure voltage between ground and terminal No. 10 (Gray/Green wire). Monitor voltage while opening main throttle valve to wide open throttle. Voltage should be one volt or less with throttle fully closed, and 10-14 volts with throttle fully open. If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
8. Turn ignition off. Disconnect TRAC ECU harness connector T13. Turn ignition on. Measure voltage between ground and terminal No. 10 (Gray/Green wire). Monitor voltage while opening main throttle valve to wide open throttle. Voltage should be one volt or less with throttle fully closed, and 10-14 volts with throttle fully open. If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
9. Turn ignition off. Check for open or short in Gray/Green wire between TRAC ECU T13 connector and ECM. Repair as needed. If circuit is okay, go to next step.
10. Inspect main TP sensor operation. See appropriate SYSTEM & COMPONENT TESTING article in ENGINE PERFORMANCE section. Adjust or replace as needed. If main TP sensor is okay, replace ECM.

DTC 47 OR 48: SUB-THROTTLE POSITION SENSOR CIRCUIT (LS400, 1997 SC300 & SC400)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

Sub-throttle position sensor detects opening angle of sub-throttle valve and sends signal to ABS/TRAC ECU. If incorrect signal is input, ABS/TRAC ECU prohibits TRAC system operation. DTC 47 is set when ABS/TRAC ECU detects zero voltage on IDL2 terminal even though sub-throttle is commanded to fully closed position during sub-throttle initial check, or ABS/TRAC ECU detects voltage for one second on IDL2 terminal during sub-throttle initial check with sub-throttle in nearly open position. DTC 48 is set when ABS/TRAC ECU detects 4.9 volts or greater on VTA2 terminal, or ABS/TRAC ECU detects .1 volt or less on VTA2 terminal. Sub-throttle position sensor signal is transmitted to TRAC ECU from Engine Control Module (ECM). If a problem occurs at engine both ECM and TRAC ECU will detect it. Possible causes are

1. Sub-throttle position sensor.
2. IDL2 open or short circuit
3. VTA2 open or short circuit
4. Engine Control Module (ECM).
5. Throttle valve motor driver.

1. For DTC 47 go to step 5). For DTC 48, determine if any engine DTCs are present. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE section. Repair as needed. If no engine DTCs are present, go to next step.
2. Remove instrument panel under cover. Turn ignition on. Remove intake air duct at throttle body. Disconnect sub-throttle valve step motor (LS400) or actuator (SC300, SC400) connector. Using voltmeter, backprobe ECM harness connector E13 (LS400) or E12 (SC300, SC400). Measure voltage between ground and terminal No. 12 (Yellow/Green wire) and No. 22 (Brown wire), or No. 63 (Red/Black wire) and No. 65 (Brown wire).
3. Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be .3-.8 volts with throttle fully closed, and 3.2-4.9 volts with throttle fully open. If voltage is within specification, replace ECM. If voltage is not within specification, go to next step.
4. Turn ignition off. Check continuity of VTA2 circuit between sub-throttle position sensor and ECM. Repair as needed. Ensure circuit is not shorted to ground. If circuit is okay, adjust or replace sub-throttle position sensor. See SYSTEM & COMPONENT TESTING article in ENGINE PERFORMANCE section.
5. Access throttle valve motor driver. Do not disconnect connectors. Remove air intake duct at throttle body. Turn ignition on. Backprobing throttle valve motor driver connector T7 (LS400) or T13 (SC300, SC400), measure voltage between ground and terminal No. 4 (Red/Black wire).
6. Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be one volt or less with throttle fully closed, and 10-14 volts with throttle fully open. If voltage is within specification, replace throttle valve motor driver. If voltage is not within specification, go to next step. NOTE: Following step may set DTCs.
7. Turn ignition off. Disconnect throttle valve motor driver connector T7 (LS400) or T13 (SC300, SC400). Measure voltage between ground and terminal No. 4 (Red/Black wire). Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be one volt or less with throttle fully closed, and 10-14 volts with throttle fully open. If voltage is within specification, replace throttle valve motor driver. If voltage is not within specification, go to next step.
8. Turn ignition off. Check continuity of IDL2 circuit between throttle valve motor driver and ECM. Repair as needed. Ensure circuit is not shorted to ground. If circuit is okay, go to next step.
9. Inspect sub-throttle position sensor operation. See appropriate SYSTEM & COMPONENT TESTING article in ENGINE PERFORMANCE section. Adjust or replace as needed. If sub-throttle position sensor is okay, replace ECM.

DTC 47 OR 48: SUB-THROTTLE POSITION SENSOR CIRCUIT (GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

Sub-throttle position sensor detects opening angle of sub-throttle valve and sends signal to ABS/TRAC ECU. If incorrect signal is input, ABS/TRAC ECU prohibits TRAC system operation. DTC 47 is set when ABS/TRAC ECU detects deviation of 5 steps or more to the closed side of idle step during sub-throttle initial check. DTC 47 is also set when ABS/TRAC ECU detects zero voltage on IDL2 terminal even though sub-throttle is commanded to fully closed position during sub-throttle initial check. DTC 47 is also set when ABS/TRAC ECU detects voltage of 1.45 volts or more on VSH terminal while idle switch is on. DTC 48 is set when TRAC ECU detects 4.9 volts or greater on VSH terminal, or TRAC ECU detects .2 volt or less on VSH terminal with IDL2 switched off. Sub-throttle position sensor signal is transmitted to TRAC ECU from Engine Control Module (ECM). If a problem occurs at engine both ECM and TRAC ECU will detect it. Possible causes are

1. Sub-throttle position sensor.
2. IDL2 open or short circuit
3. VSH open or short circuit.

Note. Clear DTC after completing repairs. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS).

1. Determine if any engine DTCs are present. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE section. Repair as needed. If no engine DTCs exist, go to next step.
2. Turn ignition on. Remove intake air duct at throttle body. Disconnect step motor connector. Using voltmeter, backprobe TRAC ECU harness connector T13. Measure voltage on terminal No. 19 (Yellow/Red wire). Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be 1.5 volts or less with throttle fully closed, and 3-4.5 volts with throttle fully open. If voltage is within specification, go to step 7). If voltage is not within specification, go to next step.
3. Turn ignition off. Check continuity of VSH circuit between TRAC ECU and ECM. Repair as needed. Ensure circuit is not shorted to ground. If circuit is okay, go to next step.
4. Disconnect ECM harness connectors. Install check connector. Remove air intake duct at throttle body. Disconnect TRAC ECU connector. Turn ignition on. Measure voltage between ground and terminal No. 39 on connector "A". Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be 1.5 volts or less with throttle fully closed, and 3-4.5 volts with throttle fully open. If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
5. Measure voltage between terminals No. 12 and 65 on check connector "B". Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be .3-.8 volts with throttle fully closed, and 3.2-4.9 volts with throttle fully open. If voltage is within specification, replace ECM. If voltage is not within specification, go to next step.
6. Turn ignition off. Check continuity of VTA2 circuit between sub-throttle position sensor and ECM. Repair as needed. Ensure circuit is not shorted to ground. If circuit is okay, adjust or replace sub-throttle position sensor.
7. Turn ignition on. Backprobing TRAC ECU harness connector T13, measure voltage between ground and terminal No. 22 (Red/Black wire). Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be one volt or less with throttle fully closed, and 10-14 volts with throttle fully open. If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
8. Turn ignition off. Disconnect TRAC ECU connector T13. Measure voltage between ground and terminal No. 22 (Red/Black wire). Monitor voltage while opening sub-throttle valve to wide open throttle. Voltage should be one volt or less with throttle fully closed, and 10-14 volts with throttle fully open. If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
9. Turn ignition off. Check continuity of IDL2 circuit between TRAC ECU and ECM. Repair as needed. Ensure circuit is not shorted to ground. If circuit is okay, adjust or replace sub-throttle position sensor.
10. Inspect sub-throttle position sensor operation. See SYSTEM & COMPONENT TESTING article in ENGINE PERFORMANCE section. Adjust or replace as needed. If sub-throttle position sensor is okay, replace ECM.

DTC 49: ENGINE COMMUNICATION CIRCUIT (GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

TR2 circuit sends ignition timing retard request signals from TRAC ECU to Engine Control Module (ECM). DTC is set when TR2 output voltage differs from TR2 monitor voltage. Possible causes are

1. TR2 open or short circuit.

Note. Clear DTC after completing repairs. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS).

1. Ensure ignition is off. Disconnect TRAC ECU harness connectors. Turn ignition on. Using voltmeter, measure voltage between ground and terminal No. 21 (Pink wire) on connector T13. If voltage is 8-14 volts, replace TRAC ECU. If voltage is not 8-14 volts, go to next step.
2. Turn ignition off. Check continuity of TR2 circuit between TRAC ECU and ECM. Repair as needed. Ensure circuit is not shorted to ground. If circuit is okay, replace ECM.

DTC 51: ENGINE MALFUNCTION DETECTION CIRCUIT

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

If an engine DTC is present, TRAC system is prevented from functioning. On GS300, DTC is set when TRAC ECU detects one volt or less on terminal TR5 with engine speed of 500 RPM or greater for more than one second. On LS400, DTC is set when 1.5 volts is detected on terminal LBL for 10 seconds or more. On SC300 and SC400, DTC is set when problem signal is detected in engine control system with engine speed of 500 RPM or greater for 7 seconds. Possible causes are

1. TR5 short circuit.
2. Engine Control System.
3. ECT System.

Determine if any engine DTCs are present. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE section. Repair as needed. If no engine DTCs exist, inspect malfunction indicator light circuit.

DTC 52: BRAKE FLUID LEVEL WARNING SWITCH CIRCUIT (EXCEPT GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

Brake fluid level warning switch sends appropriate signal to ABS/TRAC ECU when brake fluid level becomes low. DTC is set when ABS/TRAC ECU detects 1.5 volts or less on terminal LBL for 10 seconds or more. Possible causes are

1. Brake fluid level.
2. Brake fluid level warning switch.
3. Brake fluid level warning switch short circuit.
4. ABS/TRAC ECU.

1. Inspect brake fluid level. If brake fluid level is low, check brake system for fluid leakage. If brake system is okay, adjust fluid level as needed. If fluid level is okay, go to next step.
2. Inspect brake fluid level warning switch. Continuity should exist between switch component terminals when switch float is down. Replace as needed. If switch is okay, go to next step.
3. Inspect brake warning light circuit between switch and ABS/TRAC ECU for open or short. Repair as needed. If circuit is okay, replace ABS/TRAC ECU.

DTC 53: ECM COMMUNICATION CIRCUIT MALFUNCTION (EXCEPT GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

TRA circuit sends TRAC control information from ABS/TRAC ECU to Engine Control Module (ECM). EFI+ and EFI- circuits send engine control information from ECM to ABS/TRAC ECU. DTC is set when ECM receives a trouble signal in TRA circuit, or no EFI circuit data is received from ECM when engine speed is 500 RPM or greater and vehicle speed is 37 MPH or greater for 5 seconds. Possible causes are

1. TRA open or short circuit.
2. EFI+ open or short circuit.
3. EFI- open or short circuit.
4. ECM.
5. ABS/TRAC ECU.

Ensure ignition is off. Check continuity of TRA, EFI+ and EFI- circuits between ECM and ABS/TRAC ECU. Ensure circuits are not shorted to ground. Repair as needed. If all circuits are okay, replace ECM or ABS/TRAC ECU, or both.

DTC 61: ABS/TRAC ECU & TRAC ECU COMMUNICATION CIRCUIT MALFUNCTION (GS300)

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see appropriate wiring diagram in WIRING DIAGRAMS .

DTC is set when TRAC ECU loses communication with ABS/TRAC ECU. Possible causes are

1. ABSO circuit open or short circuit.
2. BRC circuit open or short circuit.
3. BRP circuit open or short circuit.

Note. Clear DTC after completing repairs. See CLEARING DIAGNOSTIC TROUBLE CODES (DTCS).

1. Access TRAC ECU. Do not disconnect harness connectors. Measure voltage by backprobing connectors. Turn ignition on. Measure voltage between ground and terminal No. 15 (Violet wire) and No. 1 (Yellow/Red wire) on connector T14, and between ground and terminal No. 23 (Gray wire) on connector T13. Voltage should be a 7 volt pulse on terminal No. 23 and 6-14 volts on terminals No. 1 and 15. If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
2. Turn ignition off. Disconnect TRAC ECU harness connectors. Turn ignition on. Repeat step 1). If voltage is within specification, replace TRAC ECU. If voltage is not within specification, go to next step.
3. Turn ignition off. Check continuity of ABSO, BRC and BRP circuits between TRAC ECU and ABS/TRAC ECU. Repair as needed. If circuits are okay, replace ABS/TRAC ECU.