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DTC P285A: Auxiliary Gearbox Gear 2 Incorrect Ratio
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines that the system is faulty when the auxiliary gearbox remains the gear ratio is abnormal although the TCM commands the 2nd gear.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • The system determines that a fault has occurred when the gear ratio is within ± 10 percent of the 1st gear ratio (1.639 - 2.003) for at least 0.5 second while the TCM is shifting the auxiliary gear to 2nd gear.
  • The system determines that a fault has occurred when the gear ratio is 0.500 or less, or 1.500 or more for at least 0.2 second while the TCM is shifting the auxiliary gear to 2nd gear.
 
 
MONITOR EXECUTION
  • Accelerator pedal opening angle: 7.8 percent or more <Only when determining whether 1st gear ratio is satisfied>
  • Vehicle speed: 10 km/h (6 mph) or more <Only when determining whether 2nd gear ratio is not satisfied>
  • 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"
  • Acceleration: -0.05G or less <Only when determining whether 2nd gear ratio is not satisfied>
  • 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: Auxiliary gearbox gear 1 incorrect ratio run-up
  • P2858: Auxiliary gearbox gear 2 incorrect ratio run-up
  • P2859: Auxiliary gearbox gear 1 incorrect ratio
  • U0001: Malfunction of CAN communication circuit (Bus off)
  • U0100: CAN time-out error (Engine)
Sensor (The sensor below is determined to be normal)
  • Transmission range switch
  • Output speed sensor
  • Secondary pulley speed sensor
  • Low brake solenoid valve
  • High clutch and reverse brake solenoid valve
 
 
LOGIC FLOW CHARTS (Monitor Sequence)
 
 
DTC SET CONDITIONS
Check Conditions
  • Target auxiliary gear position: 2nd
  • 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 volts or more (Opening angle: 7.8 percent or more)
  • Engine speed: 450 r/min or more
  • Secondary pulley speed: 300 r/min or more
  • Output speed: 300 r/min or more
Judgment Criteria
  • The actual gear ratio of the auxiliary gearbox deviates by ± 10 percent or less from the 1st gear ratio (1.639 - 2.003) for 0.5 second.
 
 
LOGIC FLOW CHARTS (Monitor Sequence)
 
 
DTC SET CONDITIONS
Check Conditions
  • Target auxiliary gear position: 2nd
  • Voltage of battery: 10 volts or more
  • Voltage of battery: 16.5 volts or less
  • Transmission range: "D" or "L"
  • Vehicle speed: 10 km/h (6 mph) or more
  • Engine speed: 450 r/min or more
  • Secondary pulley speed: 300 r/min or more
  • Output speed: 300 r/min or more
  • Acceleration: -0.05 G or less
Judgment Criteria
  • The actual gear ratio of the auxiliary gearbox deviates by ± 50 percent or more from the 2nd gear ratio (0.500 or less, 1.500 or more) for 0.2 second.
 
 
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 low brake solenoid valve)
  • Malfunction of the transaxle assembly
 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
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 low brake solenoid valve at TCM connector (LBLS terminal).
(1) Connect the CVT assembly connector.
(2) Connect an oscilloscope between TCM connector LBLS terminal and body ground (Refer to ).
(3) Transmission range: "D" range
(4) Drive at a constant speed of approximately 20 km/h (12.4 mph) (auxiliary gearbox: at 2nd gear).
(5) Use an oscilloscope, 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 volts or more and the minimum value should be 1 volt or less. There should be no noise in the output wave pattern.
Is the check result normal?
Go to Step 3.
Refer to DTC P0973: Malfunction of the low brake solenoid valve (short to ground) , or DTC P0974: Malfunction of the low brake solenoid valve (open circuit/short to power supply) .
 
STEP 3. Using scan tool (M.U.T.-III), recheck the DTC.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "LOCK" (OFF) position.
(3) Carry out a test drive with the OBD-II drive cycle pattern.
(4) Recheck the DTC.
Is DTC P285A stored?
Go to Step 4.
The trouble can be an 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 ).