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DTC P2857: Auxiliary Gearbox Gear 1 Incorrect Ratio Run-up
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines that the system is defective when the auxiliary gearbox remains at incorrect ratio although the TCM commands the 1st gear.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • The gear ratio is 2.232 or more for two seconds while the TCM is shifting the auxiliary gear to 1st gear.
 
 
MONITOR EXECUTION
  • Accelerator pedal opening angle: 7.8% 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 B
  • Target auxiliary gear position: 1st
 
 
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
  • P2858: 2nd 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 B
  • Accelerator pedal position sensor (main) output voltage: 1.23V or more (Opening angle: 7.8% 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
  • Target auxiliary gear position: 1st
Judgment Criteria
  • While the vehicle is being driven, the actual gear ratio of the auxiliary gearbox remains more than 2.232 for two seconds although the TCM commands the 1st gear.
 
 
OBD-II DRIVE CYCLE PATTERN
Accelerate to 40 km/h (24.9 mph) slowly with the accelerator opening angle at 10% or more.
 
 
PROBABLE CAUSES
  • Malfunction of the valve body assembly (Faulty line pressure 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 defective connector.
 
STEP 2. Measure the output wave pattern of the low brake solenoid valve at TCM connector (LBLS terminal).
(1) Connect the CVT assembly connector.
(2) Selector lever position: D range.
(3) Drive at a constant speed of approx. 20 km/h (auxiliary gearbox: at 1st gear)
(4) Connect an oscilloscope, and measure the voltage between TCM connector LBLS 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 diagnostic trouble code No.P0973: Low Brake Solenoid Valve (short to ground) , or diagnostic trouble code No.P0974: Low Brake Solenoid Valve (open circuit/ short to power supply) .
 
STEP 3. Symptom recheck after erasing diagnostic trouble code
(1) Erase the diagnostic trouble code.
(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 diagnostic trouble code is stored.
Is the diagnostic trouble code stored?
Go to Step 4.
Intermittent malfunction (Refer to GROUP 00 - 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 ).