NO.8 LOW MAXIMUM SPEED AND POOR ACCELERATION


8	Low maximum speed and poor acceleration
DESCRIPTION	• Vehicle acceleration is poor at start. • Delayed acceleration when accelerator pedal is depressed while driving.
POSSIBLE CAUSE	• Engine malfunction – Clogged air cleaner, inaccurate ignition timing, ignition leak, reduced compression, incorrect engine torque signal, etc. • AT malfunction – Transmission fixed in 3GR (operating fail-safe function) – Input/output signal malfunction (VSS, turbine sensor, TFT sensor, pressure control solenoid, TCC solenoid, shift solenoids A, B, C and F) • Maximum speed is low or acceleration is poor because 3GR is fixed as a fail-safe. In such cases, DTC is stored. – Improper TCM ground • Transmission is mechanically fixed in 3GR if TCM stops operating due to improper TCM ground. In such cases, DTC is stored. – Improper ground of GND return circuit at AT • If there is improper ground of GND return circuit, clutch pressure may decrease, causing clutch slippage. – Improper adjustment TR switch – Incorrect characteristic of accelerator position sensor, accelerator position signal, TP sensor, or throttle opening angle signal (CAN communication) • TP sensor and throttle opening angle signal (CAN communication) do not change in proportion to throttle opening angle. Due to this, high or low gear is fixed, resulting in low maximum speed and poor acceleration. (Refer to improper accelerator position sensor, accelerator position signal, TP sensor, throttle opening angle signal (CAN communication) in "No.11 Abnormal shifting".) – Clutch slippage (low clutch and high clutch) • In the event of clutch slippage, a DTC (incorrect gear ratio) is stored. – Reduced line pressure – Control valve body malfunction (improper operation, stuck, clogged oil passage) • Hydraulic circuit clogging (Shift solenoid A, B, C and F, and TCC solenoid) • Control valve spool malfunction – No torque generated. • Torque converter malfunction (improper operation) Note • Before following the troubleshooting steps, make sure that the Automatic Transmission On-Board Diagnostic and Automatic Transmission Basic Inspection are conducted. (See BASIC INSPECTION.)


STEP	INSPECTION		ACTION
1	With the ignition switch at the ON position, does the gear position indicator light indication correspond to the selector lever position?	Yes	Go to the next step.
1		No	Go to No.29 "GEAR POSITION INDICATOR LIGHT DOES NOT ILLUMINATE IN M RANGE", or No.30 "GEAR POSITION INDICATOR LIGHT ILLUMINATES IN D RANGE OR P, N, R POSITIONS".
2	Go to No.12 "LACK/LOSS OF POWER-ACCELERATION/CRUISE". (See NO.12 LACK/LOSS OF POWER-ACCELERATION/CRUISE.) Is the CIS system normal?	Yes	Go to the next step.
2		No	Repair or replace any malfunctioning parts.
3	Disconnect the solenoid valve connector. Does the vehicle operate as follows? D range: 3GR (fixed) R position: Reverse	Yes	Go to the next step.
3		No	Overhaul the control valve body and repair or replace any malfunctioning parts. (See AT Workshop Manual.) If the problem remains, overhaul the transmission and repair or replace any malfunctioning parts.
4	Drive the vehicle in D range. Does the vehicle start from stop in the first gear?	Yes	Go to the next step.
4		No	Inspect the following values. (See PCM INSPECTION.) (See TCM INSPECTION.) PCM PIDs (using WDS or equivalent): • APP1 • APP2 • TP_REL • VSS TCM terminal voltage: • 2G (turbine sensor) • 1D (TR switch, P position) • 2B (TR switch, N position) • 2C (TR switch, R position) • 2E (TR switch, D range) • 2K (VSS) Repair or replace any malfunctioning parts.
5	Disconnect the TCM connector. Is the resistance between terminal 2U at the TCM connector and terminal J at solenoid valve wiring harness-side connector 5.0 ohms or less?	Yes	Go to the next step.
5		No	Repair open circuit.
6	Is the resistance between ground terminal 2M or 2Q at the TCM connector and body ground 5.0 ohms or less?	Yes	Go to the next step.
6		No	Repair open ground circuit.
7	Stop the engine. Disconnect the solenoid valve connector. Measure the resistance between the following solenoid valve connector terminals. (See SOLENOID VALVE INSPECTION.) • Terminals E-J (shift solenoid A) • Terminals F-J (shift solenoid B) • Terminals H-J (shift solenoid C) • Terminals I-J (shift solenoid F) • Terminals G-J (TCC solenoid) Are the resistances normal?	Yes	Go to the next step.
7		No	Inspect for open circuit in the malfunctioning solenoid related wiring harnesses. • If the wiring harnesses are okay, inspect if the solenoids are stuck mechanically.
8	Perform the stall test. (See Stall Speed Test.) Is the stall speed normal?	Yes	Reverify symptoms of malfunction.
8		No	Overhaul the transmission and repair or replace any malfunction parts. (See AT Workshop Manual.)
9	Verify the test results. • If normal, return to the diagnostic index to service any additional symptoms. • If the malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis. – If the vehicle is repaired, troubleshooting completed. – If the vehicle is not repaired or additional diagnostic information is not available, replace the TCM. (See TCM REMOVAL/INSTALLATION.)