C1779

SUSPENSION CONTROL: AIR SUSPENSION SYSTEM: C1779/79: Crankshaft Position Sensor Circuit

DTC C1779/79 - Crankshaft Position Sensor Circuit

DTC C1797/97 - Crankshaft Position Sensor Circuit

DESCRIPTION

The suspension control ECU receives the engine speed signal from the ECM.
When inspecting by test mode, the suspension control ECU scans changes in the signals. If there is no change, it outputs the test DTC (C1797/97).





HINT: When DTC C1797/97 is output, follow the same procedure as that of DTC1779/79.

WIRING DIAGRAM





INSPECTION PROCEDURE
HINT: Start the inspection from step 1 when using the intelligent tester, and start from step 2 when not using the intelligent tester.

PROCEDURE

1. READ VALUE USING INTELLIGENT TESTER
(a) Connect the intelligent tester to the DLC3.
(b) Turn the ignition switch to the ON position, and push the intelligent tester main switch on.
(c) Select the item below in the DATA LIST, and read its value displayed on the intelligent tester.
AIRSUS:





(d) Check that there is no difference between the engine speed value output from the crankshaft position sensor displayed on the intelligent tester and the engine speed value displayed on the tachometer when driving the vehicle.
OK:
There is almost no difference in the displayed engine speed values.
HINT: There is tolerance of ± 10 % in the tachometer indication.

NG -- CHECK DTC OUTPUT
OK -- REPLACE SUSPENSION CONTROL ECU
2. CHECK DTC OUTPUT
(a) Check if the normal code is output by SFI system DTC Check / Clear.
OK:
No DTC output from SFI system.
NG -- REPAIR CIRCUIT INDICATED BY OUTPUT CODE
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (SUSPENSION CONTROL ECU - ECM)





(a) Disconnect the suspension control ECU S15 connector.
(b) Disconnect the ECM E5 connector.
(c) Measure the resistance according to the values in the table below.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. INSPECT SUSPENSION CONTROL ECU (TACH)





(a) Connect the suspension control ECU S15 connector.
(b) Connect the ECM E5 connector.
(c) Remove the ECM with connector being connected.
(d) Turn the ignition switch to the ON position.
(e) Check output waveform.
(1) Using an oscilloscope, connect the terminals, as shown in the chart below.










(2) With the engine idling, check the output waveform.
OK:
The output waveform appears as shown in the illustration.





HINT: As the engine speed becomes higher, the waveform cycle gets shorter.

NG -- REPLACE ECM
OK -- REPLACE SUSPENSION CONTROL ECU