Ch 42 Automatic Transmissions

Transfer Case

4WD vehicles may have an additional speed sensor located where?

applied, disengages

A BPP switch tells the TCM when the brakes are ___, at that time the TCC ___.

no upshifts, quick upshifts, delayed shifts, line-pressure problems, and erratic converter clutch engagement

A bad TP sensor can cause?

the gear selected by the driver

A digital transmission range (TR) sensor informs the TCM of?

low apply pressure

A faulty clutch solenoid or its return spring may cause?

the actual shift points to be used by the computer according to the input data it receives from the sensors

A shift schedule contains?

two, four

A typical 4 speed unit has ___ shift solenoids. The solenoids offer ___ possible on-off combinations to control fluid to the shift valves.

Early downshifts

A very high TP angle causes?

upshifts to occur early

A very low TP angle causes?

a scan tool check for trouble codes

All EAT diagnostics should begin with?

the clutch to not fully engage resulting in shudder and will contaminate clutch friction material

An out of round torque converter will cause?

light throttle; pressure increase

At times, a solenoid will work fine during ___ operation but may not allow the valve to exhaust enough fluid when ___.

A variator

Audi's stepless Multitronic CVT is based on?

When they are new or after the battery has been disconnected for a long period

Automatic transmissions with adaptive learning may display normal harsh and/or abrubt shifting under what conditions?

case grounded and fed voltage by the computer or if the always have power applied to them and the computer supplies the ground

Before manually activating solenoids, you must first determine if the the solenoids are?

smooth starting; slip just enough to get the car moving without stalling or straining the engine

CVT; The start clutch allows for ___ and is designed to?

It allows for limited driving capabilities and is designed to prevent further transmission damage while allowing the driver to drive with decreased power and efficiency to a service facility for repairs.

Define Limp-In mode and its purpose.

engine speed, TP sensor, engine coolant, ATF temperature, operating gear, and the time it took to shift gears.

During a road test there are several pieces of critical information given by the inputs on the scan tool. What are they?

Electronic Automatic Transmission

EAT stands for?

line pressure control system

EATs with adaptive learning capabilities have a ___ that compensates for the normal wear of a transmission.

eCVT (electronically controlled continuously variable transmission)

Ford Motor Company hybrids are equipped with?

integrated electric oil pump; different gear ratios

Honda hybrid models have an automatic transaxle that is fitted with an ___ and ___.

connect a jumper wire or use a transmission tester that allows it

How can you manually activate shift solenoids?

Ohmmeter, Voltmeter, Lab scope

How do you check a TP sensor?

scan tool, multimeter set to the Hz frequency range (normally 30Hz at idle; will increase as the throttle opens)

How do you test a MAF sensor?

propel the vehicle; constantly variable drive ratio

Hybrids; transmissions are fitted with electronic motors what both help ___ and provide a ___.

converter

If a shudder is only noticeable during the engagement of the clutch, the problem is typically in the ___.

a faulty clutch valve or control solenoid or a fault in the solenoid control circuit

If pressure did not change, but the TCC did not engage what could be the issue?

it will look at the engine temperature

If the TFT sensor fails or the TCM determines the temperature signals are incorrect, how does the TCM estimate the temperature of the ATF?

transmission kickdown shifts during acceleration as well as upshifts and downshifts

If the TP signal is wrong, it can affect?

shudder; vibration

If the clutch engages prematurely or is not applied with full pressure a ___ or ___ results from from the rapid grabbing and slipping of the clutch.

pressure loss

If the input shaft end is worn or the O-ring at the end is cut or worn, there will be ___ at the converter clutch.

replacement of the converter

If the shudder is caused by the clutch, what is required to fix the problem?

the control system

In CVT's the pulley ratios are always controlled by what?

engine; compensate for any changes in the engine's performance

In EATs with adaptive learning, the system may monitor the condition of the ___ and ___.

Monitoring the serial data with a scan tool during operation and comparing the observed values to specs

It is possible to pinpoint the exact cause of a transmission problem by?

the clutch will not fully engage

Loss of pressure at the converter clutch will cause?

Lab scope or an ohmmeter outside of the vehicle

Magnetic pulse generator speed sensors can be tested with?

smooth engagement and disengagement and allows for partial engagement of the clutch

Modulating the pressure to the clutch allows for?

variable force solenoids, pulse width modulated

Most EPC solenoids are ___ or ___ and contain a spool valve or plunger and a spring.

Valve body inside the transmission

Most manufacturers mount the TCM on the?

an ohmmeter or test light

Most mechanically or hydraulically controlled switches can be checked with?

Oil throw through the torque converter is reversed; pressure gauge

On early electronically controlled systems with a TCC solenoid, the clutch is typically applied when ___. This change can be observed with a ___.

it may be integrated in the PCM or mounted externally

On vehicles using the BARO sensor it is typically located where?

delays upshifts and increases operating pressures when the vehicle is operating with a heavy load and provides quicker downshifts during deceleration

Operational modes; What does the Tow/Haul switch do?

the TCM will control shifts normally, however if the throttle is quickly opened the shift pattern will switch to the power mode

Operational modes; What does the auto mode do?

the transmission operates according to the shift schedule and logic set for normal or regular operation

Operational modes; What does the normal mode do?

the TCM uses different logic and shift schedules to provide for better acceleration and performance with heavy loads. (normally by delaying upshifts)

Operational modes; What does the power mode do?

applying air pressure to the part that would normally be exposed to fluid pressure

Pressure switches can be tested by?

MIL

Prior to retrieving DTCs, pay attention to the ___.

a scan tool should be connected to the circuit to monitor engine and transmission operation

Road tests should be conducted the same way as one for nonelectric transmissions except?

Regulate shift timing and feel by controlling the delivery of fluid to the shift valves

Shift solenoids are used to do what and how?

adjust line pressure according to changes in altitude

Signals from the BARO sensor are used to?

an infinite reading on an ohmmeter

Solenoid windings are open when?

Inside the transmission and are mounted to the valve body

Solenoids are located where?

circuit resistance, opens, and shorts to ground

Solenoids can be checked for?

Fluid pressures, mechanical function

Solenoids simply control the ___ and do not perform ___.

Varying pulse width, signal frequency, and/or voltage levels

Some actuators are controlled by ?

Ohmmeters and lab scopes

Temperature sensors can be tested with what?

shifts to occur sooner

Temperature sensors; an overheating engine will cause?

delaying gear shifts

Temperature sensors; how can the engine's temperature be raised?

engage the converter clutch in second or third gear

Temperature sensors; if the coolant temperature rises, the computer may ___.

leaks

Testing switches with air pressure checks for?

applied, released

The BPP switch closes when the brakes are ___ and opens when they are ___.

TCM, various sensors, linear solenoids, and an inhibitor solenoid

The CVT consists of?

central processing unit, inputs, outputs

The EAT consists of?

In the air cleaner outlet tube

The IAT sensor is located?

provide the fuel injection system with mixture temperature information, determine line pressures, calculate battery temperature, and as a density correcter for airflow calculation and to proportion cold enrichment fuel flow

The IAT sensor is used to?

calculate converter turbine speed and determine the amount of T/C slip

The ISS or TSS is used to what?

injector pulse width (primarily), engine load, and to regulate EPC/shift/TCC scheduling

The MAP sensor is used to calculate?

the mass of air flowing into the engine

The MAP sensor measures?

control of TCC operation, shift timing, and fluid pressure control

The OSS is typically used for?

Cancel operation of overdrive

The TC switch allows the driver to?

momentary contact, selector lever

The TC switch is a ___switch located on the ___.

the application, modulation, and release of the TCC

The TCC solenoid is used to control?

Overdrive is cancelled

The TCIL notifies the driver that?

line pressure and shift timing

The TCM changes what to accommodate the extra engine load created by the A/C system?

reduce engine speed; maintain ideal engine temperatures

The TCM controls the pulley raitios to ___ and ___ during acceleration.

Shift timing, shift feel, and the operation of the torque converter clutch

The TCM controls?

gear changes at the optimum time

The TCM is programmed to provide?

determine the correct time to shift

The TCM uses VSS's to?

shift timing, shift feel, and TCC engagement

The TCM uses the signals from the TFT sensor to control what?

On the valve body

The TFT sensor is located?

the hydraulic throttle pressure linkage

The TP sensor is use in place of?

shift scheduling, EPC, and TCC control

The TP sensor is used for?

the drivers intent

The TP sensor sends a voltage signal to inform the TCM of?

neutral safety switch and the reverse light switch

The TR sensor normally also contains what two switches?

transmission control

The central processing unit is a separate computer designed for?

hydraulically controlled units

The clutches and bands are engaged or disengaged in the same way as?

directly from a sensor or through the CAN communication bus (connects all of the vehicle's computer systems)

The computer may receive information from two different sources, what?

the action of shift solenoids

The control unit monitors and controls?

cushion engine vibration and power surges

The damper in Toyota and Lexus Hybrids is used to?

The shift schedules and logic

The decision to shift or not to shift is based on?

the outside of the transmission at the manual lever or it may be part of the TCM

The digital TR sensor may be located on?

determine shift timing, WOT shift control, TCC control, and EPC pressure

The engine speed input is used to?

better acceleration, fuel economy, and regenerative braking

The integrated electric oil pump and different gear ratios on honda hybrid models provide?

A DMM set to measure AC voltage or an ohmmeter outside of the vehicle

The operation of a PM generator type speed sensor can be tested with?

the conventional TV cable setup

The pressure control solenoid replaces?

to provide changes in line pressure in response to engine running conditions and engine load

The purpose of the pressure control solenoid is?

smooth gear changes

The reduction in engine torque during shifting allows for ?

hydraulic pressure applied to the start clutch

The slippage in a CVT is controlled by?

transmissions clutches and bands

The solenoids do not directly control the?

the action of a motor/generator (MG1) and the torque supplied by another motor/generator (MG2), and/or the engine

The variability of the transaxle in Toyota and Lexus hybrids depends on what?

Shift timing, shift quality, fuel economy, lower exhaust emission levels, driver comfort

Through the use of electronics, transmissions have better?

PCM, momentarily alter engine output (changes ignition timing during a shift)

To control shift quality the TCM works with the ___ to?

inputs from some engine-related and driver controlled sensors

To determine the best operating strategy for the transmission, the TCM uses?

light, half, and full throttle

To totally test the transmission, you should shift gears under ___.

torque converter; clutch

Toyota and Lexus Hybrids; A damper is used in place of a ___ or ___.

A power split device that operates as a CVT without the use of belts or pulleys

Toyota and Lexus hybrids use what and how does it operate?

verification, self-monitoring, feedback

Transmission pressure switches can serve as ___ to other inputs and as ___ or ___ signals.

the action of the actuator's electrical activity

Using a lab scope on an actuator will let you observe what?

the governor signal and monitor the operation of the transmission

Voltage generating sensors serve as what and how?

no overdrive, no converter clutch engagement, no upshifts

What are the most common complaints for a bad speed sensor?

indicator lamps and solenoids

What are the two common outputs used with EATs?

they block line pressure and allow pressure to exhaust from around the shift valve which allows the valve to move

What do the shift solenoids do when they are energized?

the winding is shorted to ground

What does it mean when there is any measurable resistance when testing a solenoid with an ohmmeter?

tells the TCM that the A/C has been turned on

What does the A/C switch do?

It switches to a default, limp-in, or fail-safe mode

What does the TCM do when it detects a serious transmission, engine control, or data bus problem?

the engine runs roughly and tends to stall when the transmission is put into gear

What happens when a MAF sensor fails or sends faulty signals?

a signal is sent to the PCM to disengage overdrive operation

What happens when the TC switch is depressed?

It will stop current flow to the shift solenoid

What happens when the TCM detects a fault in a shift solenoid or its circuit?

a system consisting of three planetary gearsets coupled to two electronically controlled motors, which are powered by a 300 volt battery pack

What is a two mode transmission?

It allows the TCM to change transmission behavior based on the current condition of the transmission and engine, current operating conditions, and the habits of the driver.

What is adaptive learning in most late-model EATs?

EPC solenoid (electronic pressure control)

What is another name for the pressure control solenoid?

Position of the gear shift lever

What is the first input that the TCM looks at?

Transmission fluid pressure switch; monitors fluid pressure to determine when a clutch or band is applied or released?

What is the most commonly used pressure switch and what does it do?

To keep the TCM informed as to which hydraulic circuits are pressurized and which clutches and brakes are applied

What is the purpose of transmission pressure switches?

thermistor

What type of sensor is the TFT?

potentiometer

What type of switch is a TP sensor?

multiple pole type on/off switch

What type of switch is the TR sensor?

the engine will jerk and stall when the vehicle is stopping

What will happen if the TCC fails to release?

the engine, transmission, or another component of the driveline

When a shudder is only evident after the engagement of the clutch, the cause would be?

shift patterns, reduce excessive and harsh shifting

When cruise control is active, ___ are altered to ___.

The electronic pressure control (EPC) is adjusted by the TCM

When the A/C clutch is engaged what happens?

spool valve, decrease

When the EPC solenoid is energized it moves the ___ which ultimately causes a ___ in pressure.

spring tension, maximum

When the EPC solenoid is off, ___ keeps the valve in place to maintain ___ pressure.

TCC regulator valve, clutch

When the TCC solenoid is energized, TCC signal fluid passes to the ___ and the ___, engaging it.

exhausts, released

When the TCC solenoid is off the TCC signal fluid ___ and the converter clutch remains ___.

engine problems

Whenever diagnosing a transmission, remember that ___ can and will cause the transmission to act abnormally.

On the valve body

Where is the pressure control solenoid located?