Code No. P0791:
Malfunction of Secondary Pulley Speed Sensor
DIAGNOSTIC FUNCTION
The CVT-ECU determines whether the system is defective by monitoring the secondary pulley
speed sensor.
JUDGEMENT CRITERIA
- The status with the primary pulley speed of 1,000 r/min or more
and with the secondary pulley speed of less than 150 r/min continues for 5 seconds.
- The secondary pulley speed has dropped abruptly from 1,000 r/min or more
to 240 r/min or less. Then at least 0.5 seconds have passed with the reduced speed.
PROBABLE CAUSES
- Malfunction of secondary pulley speed sensor
- Damaged wiring harness and connectors
- Malfunction of CVT-ECU
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STEP 1. Check the following connector
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- Secondary pulley speed sensor connector
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Check the terminals for a contact status problem and internal short circuit.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair the defective connector.
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STEP 2. Check for open circuit in SGN2 line between the secondary
pulley speed sensor connector and the CVT-ECU connector
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Q.
Is the check result normal?
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Go to Step 3.
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Repair the connector(s) or the wiring harness.
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STEP 3. Voltage measurement at secondary pulley speed sensor connector
(terminal No. 1)
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(1)Disconnect the secondary pulley speed sensor connector, and measure at the wiring
harness side.
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(2)Turn the ignition switch to the "ON" position.
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(3)Measure the voltage between the secondary pulley speed sensor connector (terminal
No. 1) and body earth.
OK: 10 V or more
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Q.
Is the check result normal?
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Go to Step 4.
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NO : Repair the connector(s) or the wiring harness (power supply line between the secondary
pulley speed sensor connector terminal No. 1 and the J/B connector).
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STEP 4. Check the following connector
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Check the terminals for a contact status problem and internal short circuit.
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Q.
Is the check result normal?
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Go to Step 5.
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Repair the defective connector.
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STEP 5. Check for open circuit or short to earth in SECS line between
the secondary pulley speed sensor connector and the CVT-ECU connector
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the wiring harness.
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STEP 6. Measure the output wave pattern of the secondary pulley speed
sensor at CVT-ECU connector (SECS terminal).
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(1)Connect the secondary pulley speed sensor connector and CVT-ECU connector.
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(2)Selector lever position: D range.
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(3)Drive at a constant speed of approx. 20 km/h.
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(4)Connect an oscilloscope, and measure the voltage between CVT-ECU connector SECS
terminal and body earth.
OK: A wave pattern such as the one shown on  (Check
Procedure Using an Oscilloscope) should be output, and the maximum value should be 11 V or more
and the minimum value should be 1 V or less. There should be no noise in the output wave pattern.
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Q.
Is the check result normal?
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Go to Step 7.
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Replace the secondary pulley speed sensor.
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STEP 7. Symptom recheck after erasing diagnosis code
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Q.
Is the diagnosis code stored?
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Replace the CVT-ECU.
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunctions .).
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