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DTC P0720: Malfunction of Secondary Pulley Speed Sensor
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines whether the system is defective 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 less than 150 r/min continues for 5 seconds.
  • 0.5 seconds after the secondary pulley speed has dropped abruptly from 1,000 r/min or more to 215 r/min or less.
  • The pulley ratio is out of specifications when the engine speed, the primary pulley speed and the turbine speed are normal.
 
 
MONITOR EXECUTION
  • Transmission range: D
  • Engine speed: 450 r/min or more
  • Voltage of battery: 10 volts or more.
 
 
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • P0703: Malfunction of stoplight switch
  • P0705: Malfunction of transmission range switch
  • P0712, P0713: Malfunction of the transmission fluid temperature sensor
  • P0715: Malfunction of primary pulley speed sensor
  • P0730: Incorrect gear ratio
  • P084A: Abnormality in primary pressure sensor function
  • P0966, P0967: Malfunction of secondary pressure solenoid valve
  • P2720, P2721: Malfunction of select pressure solenoid valve
  • P2763, P2764: Malfunction of lock-up solenoid valve
  • P2765: Malfunction of turbine speed sensor
Sensor (The sensor below is determined to be normal)
  • Transmission fluid temperature sensor
  • Primary pulley speed sensor
  • Primary pressure sensor
  • Turbine speed sensor
 
 
LOGIC FLOW CHARTS (Monitor Sequence-Input Rationality-Low (Open/Low revolution))
 
 
LOGIC FLOW CHARTS (Monitor Sequence-Input Open Circuit)
 
 
LOGIC FLOW CHARTS (Monitor Sequence-Input Other Rationality)
 
 
DTC SET CONDITIONS
Check Conditions <Input Rationality-Low (Open/Low revolution)>
  • Voltage of battery: 10 volts or more.
  • Primary pulley speed: 1,000 r/min or more.
Check Conditions <Input Open Circuit>
  • Voltage of battery: 10 volts or more.
  • Secondary pulley speed at 10 millisecond before: 1,000 r/min or more.
Check Conditions <Input Other Rationality>
  • Voltage of battery: 10 volts or more.
  • Transmission range switch position: D.
  • Engine speed: 450 r/min or more.
  • Primary pulley speed: 300 r/min or more.
  • Secondary pulley speed: 300 r/min or more.
  • Turbine speed: 300 r/min or more.
  • Engine speed - Primary pulley speed: 1,000 r/min or less.
  • Turbine speed - Engine speed: 1,000 r/min or less.
  • Turbine speed - Primary pulley speed: 1,000 r/min or less.
  • Torque converter clutch status: Engaged.
Judgment Criteria <Input Rationality-Low (Open/Low revolution)>
  • Secondary pulley speed [Primary pulley speed: 1,000 r/min or more]: Less than 150 r/min. (5 seconds)
Judgment Criteria <Input Open Circuit>
  • Secondary pulley speed [Secondary pulley speed at 10 millisecond before: 1,000 r/min or more]: 215 r/min or less. (0.5 second)
Judgment Criteria <Input Other Rationality>
  • Primary pulley speed / Secondary pulley speed: More than 2.9. (5 seconds)
  • Primary pulley speed / Secondary pulley speed: Less than 0.3. (5 seconds)
 
 
OBD-II DRIVE CYCLE PATTERN
Transmission range: D (Drive the vehicle for 10 seconds or more while the accelerator opening angle is 20% or more)
 
 
PROBABLE CAUSES
  • Malfunction of secondary pulley speed sensor
  • Damaged wiring harness and connectors
  • Malfunction of TCM
 
 
DIAGNOSIS
STEP 1. Check for open circuit in ground line between the secondary pulley speed sensor connector (terminal No. 3) and body ground
Is the check result normal?
Go to Step 2.
Repair the connector(s) or the wiring harness.
 
STEP 2. 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 No. 1) and body ground.
OK: 10 V or more
Is the check result normal?
Go to Step 3.
: Repair the connector(s) or the wiring harness (power supply line between the secondary pulley speed sensor connector terminal No. 1 and the CVT control relay connector).
 
STEP 3. 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 4.
Repair the connector(s) or the wiring harness.
 
STEP 4. 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) Selector lever position: L.
(3) Drive at a constant speed of approx. 20 km/h (13 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. There should be no noise in the output wave pattern.
Is the check result normal?
Go to Step 5.
Visually check the tip of the secondary pulley speed sensor for deposits or damage, and repair or replace it if necessary.
 
STEP 5. Symptom recheck after erasing diagnostic trouble code
Is the diagnostic trouble code set?
Replace the TCM.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).