Fail Safe Operation Limp Mode 1998 Toyota Tacoma

The accelerator pedal position sensor has two (main and sub) sensor circuits. If a malfunction occurs in either of the sensor circuits, the ECM detects the abnormal signal voltage difference between the two sensor circuits and switches to limp mode. In limp mode, the functioning circuit is used to calculate the accelerator pedal opening angle to allow the vehicle to continue driving. If both circuits malfunction, the ECM regards the opening angle of the accelerator pedal as being fully closed. In this case, the throttle valve remains closed as if the engine is idling.

If a pass condition is detected and then the ignition switch is turned OFF, the fail-safe operation stops and the system returns to a normal condition.

WIRING DIAGRAM

Refer to DTC P2120 (See page ES-297).

HINT:

Read freeze frame data using an intelligent tester. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.

READ VALUE OF INTELLIGENT TESTER (ACCEL POS #1 AND ACCEL POS #2)

Connect an intelligent tester to the DLC3.

Turn the ignition switch ON and turn the tester ON.

Select the following menu items: DIAGNOSIS /

and ACCEL POS #2.

Read the values displayed on the tester.

Standard Voltage

Accelerator Pedal Operations

ACCEL POS #1 (AP#1)

ACCEL POS #2 (AP#2)

Released

G.5 to 1.1 V

1.2 to 2.G V

Depressed

2.6 to 4.5 V

3.4 to 5.G V

Go to step 3

Go to step 3

CHECK HARNESS AND CONNECTOR (ACCELERATOR PEDAL POSITION SENSOR ECM)

Wire Harness Side:

VPA2 VCPA

VCP2

VPA2 VCPA

VCP2

Accelerator Pedal Position Sensor Connector

\VPA

ECM Connector

VCP2-lm ^ VCPA

(a) Disconnect the A19 Accelerator Pedal Position (APP) sensor connector.

(b) Disconnect the E8 ECM connector.

(c) Check the resistance.

Standard Resistance (Check for open)

\VPA

Tester Connections

Specified Conditions

VPA (A19-6) - VPA (EB-1B)

Below 1 Q

EPA (A19-5) - EPA (EB-2G)

VCPA (A19-4) - VCPA (E8-26)

VPA2 (A19-3) - VPA2 (E8-19)

EPA2 (A19-2) - EPA2 (E8-21)

VCP2 (A19-1) - VCP2 (E8-27)

Standard Resistance (Check for short)

Tester Connections

Specified Conditions

VPA (A19-6) or VPA (E8-18) - Body ground

10 kQ or higher

EPA (A19-5) or EPA (E8-20) - Body ground

VCPA (A19-4) or VCPA (E8-26) - Body ground

VPA2 (A19-3) or VPA2 (E8-19) - Body ground

EPA2 (A19-2) or EPA2 (E8-21) - Body ground

VCP2 (A19-1) or VCP2 (E8-27) - Body ground

(d) Reconnect the APP sensor connector.

(e) Reconnect the ECM connector.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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Responses

  • SEPPO
    What is limp mode on tacoma?
    7 months ago
  • andrea
    How do i know if my 1998 toyota tacoma is in limp mode?
    25 days ago

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