Cranking Holding Function Circuit
3UR-FBE ENGINE CONTROL: SFI SYSTEM: Cranking Holding Function Circuit
- Cranking Holding Function Circuit
DESCRIPTION
The cranking holding control system keeps energizing the starter relay from when the ECM detects the starter signal (STSW signal) from the ignition switch until the ECM performs a judgment of "Engine started". Furthermore, the ECM outputs an accessory cut signal (ACCR signal) to the ACC cut relay during cranking to prevent flickering of the combination meter, clock, audio system, and so on.
When the ECM detects the STSW signal, the ECM outputs the starter relay drive signal (STAR signal) to the starter relay through the park/neutral position switch, and then, the engine is cranked. When the ECM receives a stable engine speed signal (NE signal), more specifically, when the NE signal reaches a predetermined value, the ECM stops outputting the STAR signal.
Also, the ECM monitors the starter relay operating conditions based on the STA terminal voltage status.
WIRING DIAGRAM
INSPECTION PROCEDURE
PROCEDURE
1. READ VALUE USING TECHSTREAM (STARTER SIGNAL)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Starter Signal.
(e) Check the result when the ignition switch is turned to ON and START positions.
OK:
Result
B -- INSPECT ECM (STSW TERMINAL VOLTAGE)
A -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Symptom Related Diagnostic Procedures
2. INSPECT ECM (STSW TERMINAL VOLTAGE)
(a) Disconnect the ECM connector.
(b) Perform the cranking operation.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
HINT
DTCs related to the communication with other computers may be set due to this inspection. Clear those DTCs after the inspection.
NG -- INSPECT IGNITION SWITCH
OK -- Continue to next step.
3. INSPECT ECM (STAR TERMINAL OUTPUT VOLTAGE)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the All Cylinders Fuel Cut.
(e) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
HINT
* The junction connector is in the engine room connector holder block as the illustration above.
* During this inspection, all connectors and relays should be connected.
NG -- INSPECT PARK/NEUTRAL POSITION SWITCH ASSEMBLY
OK -- Continue to next step.
4. INSPECT PARK/NEUTRAL POSITION SWITCH ASSEMBLY
(a) Disconnect the Park/Neutral Position (PNP) switch connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- REPLACE PARK/NEUTRAL POSITION SWITCH ASSEMBLY Removal
OK -- Continue to next step.
5. CHECK HARNESS AND CONNECTOR (PNP SWITCH - ECM)
(a) Disconnect the PNP switch connector.
(b) Disconnect the 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 -- Continue to next step.
6. CHECK HARNESS AND CONNECTOR (PNP SWITCH - ECM - ST RELAY)
(a) Remove the ST relay from the engine room relay block.
(b) Disconnect the PNP switch connector.
(c) Disconnect the ECM connector.
(d) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPAIR OR REPLACE STARTER CIRCUIT (STARTER - ST RELAY)
7. INSPECT IGNITION SWITCH
(a) Remove the ignition switch.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- REPLACE IGNITION SWITCH Removal
OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (IGNITION SWITCH - ECM)
8. INSPECT PARK/NEUTRAL POSITION SWITCH ASSEMBLY
(a) Disconnect the PNP switch connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- REPLACE PARK/NEUTRAL POSITION SWITCH ASSEMBLY Removal
OK -- Continue to next step.
9. CHECK HARNESS AND CONNECTOR (PNP SWITCH - IGNITION SWITCH AND ECM)
(a) Disconnect the ignition switch connector.
(b) Disconnect the PNP switch connector.
(c) Disconnect the ECM connector.
(d) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
HINT
The wire between the PNP switch and the ignition switch has a diode (refer to the wiring diagram). The current flowing to the PNP switch is rectified by the diode.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
10. CHECK HARNESS AND CONNECTOR (PNP SWITCH - ECM - ST RELAY)
(a) Remove the ST relay from the engine room relay block.
(b) Disconnect the PNP switch connector.
(c) Disconnect the ECM connector.
(d) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM Removal