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DTC P0791: Malfunction of Secondary Pulley Speed Sensor
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines whether the system is faulty by monitoring the secondary pulley speed sensor.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • The status with the primary pulley speed of 1,000 r/min or more and with the secondary pulley speed of 150 r/min or less continues for five seconds.
  • When the secondary pulley speed has dropped abruptly from 1,000 r/min or more to 240 r/min or less, and then it keeps 240 r/min or less for 0.5 seconds continuously.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • P0715: Malfunction of the primary pulley speed sensor
Sensor (The sensor below is determined to be normal)
  • Primary pulley speed sensor
 
 
LOGIC FLOW CHARTS [Monitor Sequence-Input Rationality Low (Open/Low Revolution)]
 
 
LOGIC FLOW CHARTS (Monitor Sequence-Input Open Circuit)
 
 
DTC SET CONDITIONS
Check Conditions
  • Voltage of battery: 10 volts or more
  • Voltage of battery: 16.5 volts or less
Judgment 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.
 
 
OBD-II DRIVE CYCLE PATTERN
The vehicle is driven for at least 10 seconds with the engine speed at 1,500 r/min or more.
 
 
PROBABLE CAUSES
  • Malfunction of secondary pulley speed sensor
  • Damaged wiring harness and connectors
  • Malfunction of TCM
 
 
DIAGNOSIS
STEP 1. Check the following connector.
  • Secondary pulley speed sensor connector
Check the terminals for a contact status problem and internal short circuit.
Is the check result normal?
Go to Step 2.
Repair the faulty connector.
 
STEP 2. Check for open circuit in SGN2 line between the secondary pulley speed sensor connector and the TCM connector.
Is the check result normal?
Go to Step 3.
Repair the connector(s) or the wiring harness.
 
STEP 3. Voltage measurement at secondary pulley speed sensor connector (terminal No. 1).
(1) Disconnect the secondary pulley speed sensor connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between the secondary pulley speed sensor connector (terminal number 1) and body ground.
OK: 10 V or more
Is the check result normal?
Go to Step 4.
Repair the connector(s) or the wiring harness (power supply line between the secondary pulley speed sensor connector terminal number 1 and the J/B connector).
 
STEP 4. Check the following connector.
  • TCM connector
Check the terminals for a contact status problem and internal short circuit.
Is the check result normal?
Go to Step 5.
Repair the faulty connector.
 
STEP 5. Check for open circuit or short to ground in SECS line between the secondary pulley speed sensor connector and the TCM connector.
Is the check result normal?
Go to Step 6.
Repair the wiring harness.
 
STEP 6. Measure the output wave pattern of the secondary pulley speed sensor at TCM connector (SECS terminal).
(1) Connect the secondary pulley speed sensor connector and TCM connector.
(2) Transmission range: "D" range
(3) Drive at a constant speed of approximately 20 km/h (12.4 mph).
(4) Connect an oscilloscope, and measure the voltage between TCM connector SECS terminal and body ground.
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.
Is the check result normal?
Go to Step 7.
Replace the secondary pulley speed sensor (Refer to GROUP 23B, Transaxle ).
 
STEP 7. Symptom recheck after erasing DTC.
Is the DTC stored?
Replace the TCM (Refer to ).
Intermittent malfunction (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).