Lexus NX: Terminals Of Ecu

TERMINALS OF ECU

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Disconnect the I51 and I53 certification ECU (smart key ECU assembly) connectors.

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

HINT:

Measure the values on the wire harness side with the connector disconnected.

Tester Connection

Input/Output

Wiring Color

Terminal Description

Condition

Specified Condition

Related Data List Item

I51-2 (STP1) - Body ground

Input

B - Body ground

Stop light switch signal

Brake pedal depressed → Brake pedal released

9 V or higher → 1 V or less

Stop Light Switch1

I53-10 (+B) - I53-11 (E)

Input

W - W-B

Power source

Always

11 to 14 V

-

I53-23 (SLP) - I53-11 (E)

Input

GR - W-B

Steering lock position signal

Steering locked

10 kΩ or higher

Steering Unlock Switch

I53-22 (P) - I53-11 (E)

Input

B - W-B

P position signal

Shift lever in P → Shift lever not in P

30 kΩ or higher → Below 200 Ω

Shift P Signal

I53-11 (E) - Body ground

-

W-B - Body ground

GND

Always

Below 1 Ω

-

I53-18 (SSW2) - Body ground

Input

G - Body ground

SSW2 contact signal

HINT:

Backup for SSW1. Behaves the same way as SSW1.

Power switch pushed → Power switch not pushed

Below 15 Ω → 10 kΩ or higher

Start Switch2

I53-16 (SSW1) - Body ground

Input

LG - Body ground

SSW1 contact signal

Power switch pushed → Power switch not pushed

Below 15 Ω → 10 kΩ or higher

Start Switch1

I53-9 (ACCD) - Body ground

Output

L - Body ground

ACC signal

20°C (68°F)

130.92 to 190.74 Ω

ACC Relay Monitor

I51-3 (IG1D) - Body ground

Output

W - Body ground

IG signal

20°C (68°F)

87.32 to 127.14 Ω

IG Relay Monitor (Outside)

I51-4 (CUTB) - I53-11 (E)

Input

P - W-B

Dark current cut pin*1

Always

11 to 14 V

-

I53-5 (SPD) - Body ground

Input

G - Body ground

Vehicle speed signal

Always

30 kΩ or higher

Vehicle Speed Signal

  • *1: In order to prevent the vehicle auxiliary battery from being depleted when the vehicle is shipped long distances, a fuse that cuts unnecessary electrical load while the vehicle is being shipped is set in the circuit. If the fuse is removed, the circuit becomes open. If the fuse that is between the vehicle auxiliary battery and terminal CUTB is removed and the circuit is open, the certification ECU (smart key ECU assembly) changes to a certain control mode (example: the transmission of electric waves every 0.25 seconds that form the detection area stops).

(c) Reconnect the I53 and I51 certification ECU (smart key ECU assembly) connectors.

(d) Measure the voltage and check for pulses according to the value(s) in the table below.

Tester Connection

Input/Output

Wiring Color

Terminal Description

Condition

Specified Condition

Related Data List Item

I51-2 (STP1) - I53-11 (E)

Input

B - W-B

Stop light switch signal

Brake pedal released → Brake pedal depressed

1 V or less → 9 V or higher

Stop Light Switch1

I53-23 (SLP) - I53-11 (E)

Input

GR - W-B

Steering lock position signal

Steering locked → Steering unlocked

11 to 14 V → 1.5 V or less

Steering Unlock Switch

I53-24 (SLR+) - I53-11 (E)

Output

L - W-B

Steering lock motor operation command signal

(Steering lock motor operation permission signal sent from the certification ECU (smart key ECU assembly))

When a door is opened, the steering lock motor will be operated if all of the following conditions are met:

  • The steering is unlocked.
  • The power switch is off.
  • The shift lever is in P.

Pulse generation

(See waveform 1)

-

I53-22 (P) - I53-11 (E)

Input

B - W-B

P position signal

Shift lever in P → Shift lever not in P

9 V or higher → 2.76 V or less

Shift P Signal

I53-18 (SSW2) - I53-11 (E)

Input

G - W-B

SSW2 contact signal

HINT:

Backup for SSW1. Behaves the same way as SSW1.

Power switch not pushed → Power switch pushed

9 V or higher → 1 V or less

Start Switch2

I53-16 (SSW1) - I53-11 (E)

Input

LG - W-B

SSW1 contact signal

Power switch not pushed → Power switch pushed

9 V or higher → 1 V or less

Start Switch1

I53-9 (ACCD) - I53-11 (E)

Output

L - W-B

ACC signal

Power switch off → Power switch on (ACC)

1 V or less → 8.5 V or higher

ACC Relay Monitor

I51-3 (IG1D) - I53-11 (E)

Output

W - W-B

IG signal

Power switch on (ACC) → Power switch on (IG)

1 V or less → 9 V or higher

IG Relay Monitor (Outside)

I53-5 (SPD) - I53-11 (E)

Input

G - W-B

Vehicle speed signal

Vehicle being driven at approx. 5 km/h (3 mph)

Pulse generation

(See waveform 2)

Vehicle Speed Signal

I51-12 (ST2) - I53-11 (E)

Output

LG - W-B

STSW signal

With the brake pedal depressed, the power switch is pressed and held → After approx. 3 sec. has elapsed, the power switch is released

9 V or higher → 1 V or less

-

HINT:

  • The waveform of the steering lock actuator motor stopped can be checked without performing any particular operation.
  • The waveform of the steering lock actuator motor operating can be checked if either of the following operations is performed:
    • To unlock the steering, bring the electrical key transmitter sub-assembly into the cabin and turn the power switch on (ACC) or on (IG).
    • To lock the steering, open a door with the power switch off and the shift lever in P.

(e) Using an oscilloscope, check the waveform of the ECU.

NOTICE:

The oscilloscope waveform shown in the illustration is an example for reference only. Noise, chattering, etc. are not shown.

(1) Waveform 1

Item

Content

Tester Connection

I53-24 (SLR+) - I53-11 (E)

Tool Setting

2 V/DIV., 200 ms./DIV.

Condition

Steering lock motor stopped → Steering lock motor operating → Steering lock motor stopped

*a

Steering lock motor not operating

*b

Steering lock motor operating

(2) Waveform 2

Item

Content

Tester Connection

I53-5 (SPD) - I53-11 (E)

Tool Setting

5 V/DIV., 200 ms./DIV.

Condition

Vehicle being driven at approx. 5 km/h (3 mph)

HINT:

The wavelength becomes shorter as the vehicle speed increases.

CHECK STEERING LOCK ECU (STEERING LOCK ACTUATOR ASSEMBLY)

Click here

CHECK ID CODE BOX (IMMOBILISER CODE ECU)

Click here

CHECK POWER SWITCH

Click here

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