Open Circuit in IG1/IG2 Power Source Circuit (C1242)
If there is a problem with the master cylinder solenoid (skid control ECU) power supply circuit, the skid control ECU stores DTCs and prohibits operation under the fail-safe function.
If the voltage supplied to the IG2 terminal is within the DTC detection range due to malfunctions in components such as the battery and generator circuit, this DTC is stored.
DTC Code | DTC Detection Condition | Trouble Area |
|---|---|---|
C1242 |
The vehicle speed is 3 km/h or more and the voltage at the ECU IG2 terminal remains below 6.5 V for more than 7 seconds. |
|
CAUTION / NOTICE / HINT
NOTICE:
- When replacing the master cylinder solenoid, perform calibration (See page
). - Inspect the fuses for circuits related to this system before performing the following inspection procedure.
CHECK TERMINAL VOLTAGE (IG2)
(a) Disconnect the A7 skid control ECU connector.
(b) Measure the voltage according to the value(s) in the table below. Standard Voltage:
|
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| NG | ![]() | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
CHECK HARNESS AND CONNECTOR (GND1, GND2 AND GND3 TERMINAL)
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| NG | ![]() | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
RECONFIRM DTC
(a) Clear the DTCs (See page
).
(b) Turn the ignition switch off.
(c) Check if the same DTC is output (See page
).
HINT:
Reinstall the sensors, connectors, etc. and restore the previous vehicle conditions before rechecking for DTCs.
ResultResult | Proceed to |
|---|---|
DTC is output |
A |
DTC is not output |
B |
| A | ![]() | REPLACE MASTER CYLINDER SOLENOID |
| B | ![]() | USE SIMULATION METHOD TO CHECK |
Test yourself
A quick Toyota 4Runner quiz: every answer comes with an explanation and a link to the manual page.

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