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DTC P2858: Auxiliary Gearbox Gear 2 Incorrect Ratio Run-up
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines that the system is faulty when the auxiliary gearbox remains at incorrect ratio although the TCM commands the 2nd gear.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • The gear ratio is 2.232 or more for at least 2 seconds while the TCM is shifting the auxiliary gear to 2nd gear.
 
 
MONITOR EXECUTION
  • Accelerator pedal opening angle: 7.8 percent or more
  • Engine speed: 450 r/min or more
  • Output shaft speed: 300 r/min or more
  • Secondary pulley speed: 300 r/min or more
  • Transmission range: "D" or "L"
  • Target auxiliary gear position: 2nd
 
 
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • P0705: Malfunction of the transmission range switch
  • P0720: Malfunction of the output speed sensor
  • P0791: Malfunction of the secondary pulley speed sensor
  • P0973, P0974: Malfunction of the low brake solenoid valve
  • P0976, P0977: Malfunction of the high clutch and reverse brake solenoid valve
  • P2857: 1st gear neutral malfunction
  • P2859: 1st gear ratio malfunction
  • P285A: 2nd gear ratio malfunction
  • U0001: Malfunction of CAN communication
  • U0100: CAN time-out error (engine)
Sensor (The sensor below is determined to be normal)
  • Transmission range switch
  • Secondary pulley speed sensor
  • Output speed sensor
  • Low brake solenoid valve
  • High clutch and reverse brake solenoid valve
 
 
LOGIC FLOW CHARTS (Monitor Sequence)
 
 
DTC SET CONDITIONS
Check Conditions
  • Voltage of battery: 10 volts or more
  • Voltage of battery: 16.5 volts or less
  • Transmission range: "D" or "L"
  • Accelerator pedal position sensor (main) output voltage: 1.23 V or more (Opening angle: 7.8 percent or more)
  • Engine speed: 450 r/min or more
  • Output speed: 300 r/min or more
  • Secondary pulley speed: 300 r/min or more
  • Target auxiliary gear position: 2nd
Judgment Criteria
  • While the vehicle is being driven, the actual gear ratio of the auxiliary gearbox remains more than 2.232 for 2 seconds although the TCM commands the 2nd gear.
 
 
OBD-II DRIVE CYCLE PATTERN
Drive at 40 km/h (24.9 mph) for at least five seconds with the accelerator opening angle at 10 percent or more.
 
 
PROBABLE CAUSES
  • Malfunction of the valve body assembly (Faulty high clutch and reverse brake solenoid valve)
  • Malfunction of the transaxle assembly
 
 
DIAGNOSIS
STEP 1. Check the following connector.
  • CVT assembly 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. Measure the output wave pattern of the high clutch and reverse brake solenoid valve at TCM connector (HRLS terminal).
(1) Connect the CVT assembly connector.
(2) Transmission range: "D" range
(3) Drive at a constant speed of approximately 20 km/h (12.4 mph) (auxiliary gearbox: at 2nd gear).
(4) Connect an oscilloscope, and measure the voltage between TCM connector HRLS 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 3.
Refer to DTC P0976: High Clutch and Reverse Brake Solenoid Valve (short to ground) , or DTC P0977: High Clutch and Reverse Brake Solenoid Valve (open circuit/ short to power supply) .
 
STEP 3. Symptom recheck after erasing DTC.
(1) Erase the DTC.
(2) Turn the ignition switch to the "LOCK" (OFF) position, and then wait for one minute. Then drive the vehicle until the engine has been warmed up.
(3) Check if the DTC is stored.
Is the DTC stored?
Go to Step 4.
Intermittent malfunction (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
 
STEP 4. CVT belt inspection.
Check the appearance of the CVT belt. (Refer to On-vehicle Service – CVT Belt Inspection)
Is the CVT belt normal?
Replace valve body assembly. (Refer to ).
Replace the transaxle assembly (Refer to ).