C2194

TIRE AND WHEEL: TIRE PRESSURE WARNING SYSTEM: C2194/94: Engine Speed Signal Error (Test Mode DTC)

DTC C2194/94 - Engine Speed Signal Error (Test Mode DTC)

DESCRIPTION

The tire pressure warning ECU receives an engine speed signal from the ECM. This DTC is stored upon entering test mode, and cleared when an engine speed signal of 1000 rpm or more is detected for 3 seconds or more. This DTC is output only in test mode.

WIRING DIAGRAM

INSPECTION PROCEDURE
NOTICE:
- 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 Programming and Relearning of the transmitter IDs into the tire pressure warning ECU after the ECU has been replaced.

PROCEDURE

1. READ VALUE USING TECHSTREAM (ENGINE SPEED)
(a) Turn the ignition switch off.
(b) Connect a Techstream to the DLC3.
(c) Turn the ignition switch ON and the tester ON.
(d) Enter the following menus: Chassis / Tire Pressure Monitor / Data List
(e) Check that the values indicated on the tester and on the combination meter are the same.

Tire Pressure Monitor

OK:
Engine speed indicated on the tester and on the combination meter are the same.
NG -- INSPECT TIRE PRESSURE WARNING ECU (TACH SIGNAL)
OK -- USE SIMULATION METHOD TO CHECK
2. INSPECT TIRE PRESSURE WARNING ECU (TACH SIGNAL)

(a) Disconnect the E74 ECU connector.
(b) Start the engine.
(c) Check the waveform of the ECU connector using an oscilloscope, while idling the engine.
OK:

Tool Setting

HINT: The wavelength becomes shorter as the engine speed increases.

NG -- CHECK HARNESS AND CONNECTOR (TIRE PRESSURE WARNING ECU - ECM)
OK -- REPLACE TIRE PRESSURE WARNING ECU
3. CHECK HARNESS AND CONNECTOR (TIRE PRESSURE WARNING ECU - ECM)

(a) Disconnect the E74 ECU connector.
(b) Disconnect the E46 ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM