Service Manual2004 ZF 4 HP 16 AUTOMATIC TRANSAXLE

SECTION 5A

ZF 4 HP 16 AUTOMATIC TRANSAXLE

Caution : Disconnect the negative battery cable before removing or installing any electrical unit or when a tool or equipment could easily come in contact with exposed electrical terminals. Disconnecting this cable will help prevent personal injury and damage to the vehicle. The ignition must also be in LOCK unless otherwise noted.

INTRODUCTION

ZF 4HP16 AUTOMATIC TRANSAXLE

The ZF 4 HP 16 is a four-speed automatic transaxle designed for cars with front-wheel drive and a transversely mounted engine.

The transaxle has a hydrodynamic torque converter with a controlled slip lock-up clutch.

A planetary gear train establishes the mechanical gear ratios. The integral constant ratio can be adapted to the engine's power output and the vehicle's weight. The electronic-hydraulic control makes controlled power shifts and various shift programs possible. In selector lever position "P", the output is locked mechanically. The special feature of this transaxle is that it operates without freewheels. Shifting between individual gears takes place by means of overlapping clutch engagement and release.

The advantage of overlap shifting is as follows:

The transaxle can be of more compact design and is lighter on account of the absence of freewheels and the lower number of shift elements
Lower drag losses, i.e. higher efficiency
Lower peak torques acting on the components and driveline.

However, overlap shifting necessitates high-performance hardware and software, and precision engine signals.

TRANSAXLE COMPONENT

DESCRIPTION AND OPERATION

The ZF 4HP 16 automatic transaxle consists primarily of the following components.

Mechanical

Torque converter with LOC
Drive link assembly
Two multiple disk clutch assemblies : clutch B,E
Three multiple brake assemblies : brake C,D,F
Lock-up clutch valve
Two planetary gear sets
One oil pump
Final drive and differential assembly

Electronic

Two shift solenoid valve(sol.1,2)
Four pressure control solenoid valve(EDS)
Tow speed sensor; A/T ISS and A/T OSS
Fluid temperature sensor
Automatic transaxle control module(TCM)
Wiring harness assembly

MECHANICAL COMPONETS

Torque converter

The converter consists of the impeller, the turbine wheel, the reaction member (stator) and the oil to transmit torque. The impeller, which is driven by the engine, causes the oil in the converter to flow in a circular pattern. This oil flow meets the turbine wheel, where is direction of flow is deflected. At the hub, the oil leaves the turbine and reaches the reaction member (stator), where it is once again deflected so that it reaches the impeller at the correct angle of flow.

The reversal effect generates moment in the stator, the reaction torque of which amplifies the turbine torque.

The ratio between turbine torque and torque is referred to as torque multiplication.

The greater the difference is speed between the pump and turbine, the greater the torque multiplication; it is at its highest when the turbine is at a standstill. The higher the speed of the turbine, the lower the torque multiplication.

When the turbine speed reaches about 85% of the pump speed, torque multiplication = 1, i.e. the turbine torques is equivalent to pump torque.

The stator, which bears against the housing via the freewheel, is then rotating freely in the oil flow and the freewheel is over-come. From this point onwards, the converter acts as a straightforward fluid coupling.

Space behind lock-up clutch piston

Friction lining
Lock-up clutch piston
Converter cover
Turbine wheel
Impeller
Stator
Turbine hub
Torque converter impeller hub

Lock-up clutch (LUC)

The converter lock-up clutch is a device, which eliminates converter slip and thus helps to improve fuel consumption.

The previous control principle for converter lock-up clutch operation has been replaced by a controlling function on the 4 HP 16. The converter lock-up clutch is engaged and released in a controlled manner. During the controlled phase, a slight speed difference between the impeller and turbine wheel is established. This ensures that the engine's rotating vibration is not phased on to the transaxle. The result is optimum shift quality.

An electronic pressure-regulating valve determines pressure regulation of the converter lock-up clutch's piston.

When open (conversion range), the oil pressure behind the converter lock-up clutch piston and in the turbine zone is equal. The direction of flow is through the turbine shaft and through the space behind the piston, to the turbine chamber.

To engage the lock-up clutch, the direction of flow is modified (reversed) via a valve in the hydraulic selector unit. At the same time, the space behind the lock-up clutch piston is vented. The oil pressure passes from the turbine chamber to the lock-up clutch piston and presses it against the converter's cover. The turbine is thus blocked by way of the linings between the piston and cover, and permits rigid through drive with no slip (or reduced slip if controlled) to the mechanical stage of the transaxle.

Fluid pump

The fluid pump is located between the torque converter and the transaxle case and is driven directly by the torque converter. The pump sucks the fluid through a filter and delivers it to the main pressure regulator valve of the control system. Excess fluid flows back to the pump. The fluid pump fulfills the following functions:

Generates line pressure.
Delivers fluid under pressure to the torque converter, thus preventing air bubbles in the fluid.
Induces a flow of fluid through the torque converter in order to eliminate heat.
Supplies fluid pressure to the hydraulic control system.
Supplies fluid pressure to the shift components.
Lubricates the transaxle with fluid.

Pump housing

Disc
Shaft seal
Stator shaft
Pump wheel
Pump ring gear
Dowel pin

Planetary gears

The ZF 4HP 16 automatic transaxle is equipped with a one sun gear, 4 planetary gears, planetary carrier, ring gear.

Each gears are located one directly behind the other and are linked together. In other words, front ring gear is permanently linked to rear planet carrier, front planet carrier is linked to rear ring gear.

The individual gear ratios are obtained by linking together the gear set elements in different ways by means of clutches and brakes.

On the 4HP 16, the power flow is directed into the planetary gear set via rear planet carrier or rear sun gear, or via both simultaneously, depending on the gear in question. The output is always via front planet carrier.

Shift elements: multi-disc clutches and brakes

The purpose of the shift elements is to perform shifts under load without the tractive flow being interrupted.

The shift elements consist of the following.

snap ring
steel disc
lined disc
cup spring
baffle plate
disc carrier
input shaft
oil supply to dynamic pressure equalizer
oil supply to clutch
cylinder
piston
spring disc

The shift elements are engaged hydraulically. The pressurized oil reaches the space between the cylinder and piston, as a result of which the discs are compressed.

The clutch/brake is engaged. When the oil pressure drops, the cup spring acting on the piston presses the piston back into its initial position. The clutch/brake is now released again.

Depending on the gear, the multi-disc clutches B and E supply the engine torques to the planetary gear train, with multi-disc brakes C, D and F directing the torque into the housing.

The dynamic pressure at clutches B and E is equal; i.e. the dynamic pressure in front of and behind the piston is equal. This equalizing effect is achieved in the following way.

The space between the baffle plate and piston is filled with unpressurised oil. A dynamic pressure dependent on the engine speed builds up. The space between pressure also builds up. However, there is simultaneously a static pressure, which causes the clutch to engage. If the static pressure is relieved, the cup spring is able to force the piston back into its original position. The advantages of this dynamic pressure equalization are:

Reliable clutch opening in all speed ranges
Smoother shifts.

Parking lock

The parking lock is actuated via the selector lever when in position P. It protects the vehicle mechanically against rolling away.

The stop plate is actuated by the selector shaft, which is permanently connected to the selector lever via a pull cable. The parking lock pawl in the parking lock gear, which is welded onto the lateral shaft of the transaxle.

This blocks the driven wheels.

Pawl
Supporting bolt
leg spring

Valve body

Valve body performs the following tasks:

Generates the line pressure needed for actuating the shift elements.
Actuates the individual shift elements via the clutch valves.
Assures limited operation of the automatic transaxle in the event of the electronics failing.
Actuating the lock-up clutch.
Generating the lubricating pressure for the transaxle

ELECTRONICAL COMPONETS

Selector lever/program switch

The driver engages the travel position via the selector lever:

P : park position

R : reverse

N : neutral

D : forward speeds

Park/Neutral Position Switch

The Park/Neutral Position Switch is located on the selector shaft and informs the TCM of the current selector lever position P-R-N-D-3-2-1.

The selector lever position is transmitted to the TCM in encoded form along 4 lines. The encoding is such that malfunctions in the connecting lead are identified.

The Park/Neutral Position Switch is located on the selector shaft, which is connected to the selector lever via a pull cable. In addition, the Park/Neutral Position Switch controls the starter interlock, the reversing light and the selector lever position indicator on the instrument panel.

Signal combination

.	L1	L2	L3	L4
. P	0	0	12	0
. R	0	0	0	12
. N	0	12	0	0
. D	12	12	12	0
. 3	12	12	0	12
. 2	12	0	12	12
. 1	0	12	12	12

Automatic transaxle output speed sensor (A/T OSS)

The vehicle A/T OSS is a magnetic inductive pickup that relays information relative to vehicle speed to the TCM.

Vehicle speed information is used by the TCM to control shift timing, line pressure, and LUC (lock-up clutch) apply and release.

The output speed sensor mounts in the case at the speed sensor rotor, which is pressed onto the spur gear. An air gap of 0.1mm~1.3mm(0.004~0.05in) is maintained between the sensor and the teeth on the spur gear teeth. The sensor consists of a permanent magnet surrounded by a coil of wire.

As the differential rotates, an AC signal is induce a higher frequency and voltage measurement at the sensor. Sensor resistance should measure ∞ at 20°C(68°F). Sensor can measure from 20HZ~8,000HZ.

Automatic transaxle input speed sensor (A/T ISS)

The A/T ISS is a magnetic inductive pickup that relays information relative to transaxle input speed to the TCM.

The TCM uses transaxle input speed information to control line pressure, LOC apply and release and transaxle shift patterns. This information is also uses to calculate the appropriate operating gear ratios and LOC slippage.

The input speed sensor mounts onto piston B that is inside of valve body.

An air gap of 1.8~2.2mm(0.07~0.086inch) is maintained between the sensor and the piston B.

The sensor consists of a permanent magnet surround by a coil of wire. As the piston B is driven by the turbine shaft, an AC signal induced in the input speed sensor.

Higher vehicle speeds induce a higher frequency and voltage measurement at the sensor.

Sensor resistance should measure between 825~835 ohms at 20°C(68°F). Sensor can measure from 1,000~8,000HZ.

Shift solenoid valve: Solenoid 1,2

The shift solenoids are two identical, normally open electronic exhaust valve that control upshifts and down-shifts in all forward gear ranges. These shift solenoids works together in a combination of ON and OFF sequences to control the line pressure and shift mechanisms (clutches, brakes).

Solenoid 1 control the high or low of the line pressure (flow to each clutch valve) by the operation type (ON/ OFF), i.e. solenoid 1is ON, line pressure will be low (6~8bar), solenoid 1 is OFF, line pressure will be high (16~18bar).

Solenoid 2 controls the oil flow to clutch valve E or lockup clutch valve by the ON/OFF signal.

The TCM monitors numerous inputs to determine the appropriate solenoid state combination and transaxle gear for the vehicle operating conditions.

Gear	Solenoid 1	Solenoid 2
Park, Neutral	ON	ON
First	ON/OFF	ON
Second	ON/OFF	OFF
Third	ON/OFF	OFF
Fourth	ON/OFF	OFF
Reverse	ON/OFF	ON

.	Line pressure	Resistance
Solenoid valve 1/Solenoid valve 2	ON (low) : 6.2~6.8bar OFF (high) 15.3~17.4 6bar	26.5 ± 0.5ohm

Pressure control solenoid valve (EDS VALVE 3,4,5,6)

The pressure control valve (EDS valve 3,4,5,6) is a precision electronic pressure regulator that controls the operations of each clutches, brakes, lock-up clutch.

The valve reduces the system pressure with which the downstream solenoid valves and electrical pressure regulating valves are charged. It is possible to sue smaller solenoid valves as a result. The EDS require a constant input pressure.

Transaxle Fluid Temperature (TFT) Sensor

The TFT sensor is a positive temperature coefficient thermistor (temperature sensitive resistor) that provides information to the TCM regarding transaxle fluid temperature. The temperature sensor is located in valve body. Calculated temperature is a factor to determine at the shift time and shift delay time.

The internal electrical resistance of the sensor varies in relation to the operating temperature of the transaxle fluid (see chart).

The TCM sends a 5volt-reference signal to the temperature sensor and measures the voltage rise in the electrical circuit. A higher fluid temperature creates a higher resistance in the temperature sensor, thereby measuring a lower voltage signal.

The TCM measures this voltage as another input to help control line pressure, shift schedules and LOC apply. When transaxle fluid temperature reaches 140°C (284°F) the TCM enters "hot mode". Above this temperature the TCM modifies transaxle shift schedules and LOC apply in an attempt to reduce fluid temperature by reducing transaxle heat generation. During hot mode the TCM applies the LOC at all times in fourth gears. Also, the TCM performs the 2-3 and 3-4 shifts earlier to help reduce fluid heat generation. Hot mode may not be available on some applications.

Transaxle Sensor - Temperrature To Resistance To Voltage (approximate)
°C	R hight (ohms)	R low (ohms)	°C	R hight (ohms)	R low (ohms)
-40	586	556	50	1,206	1,173
-30	641	611	60	1,295	1,256
-20	699	670	70	1,388	1,341
-10	760	732	80	1,485	1,430
0	825	799	90	1,585	1,522
10	893	868	100	1,690	1,617
20	963	942	110	1,798	1,715
25	1,000	980	120	1,910	1,816
30	1,039	1,017	130	2,025	1,920
.	.	.	140	2,145	2,027

Transaxle electrical connector

The transaxle electrical connector is a very important part of the transaxle operating system. Any interference with the electrical connection can cause the transaxle to set Diagnostic Trouble Codes (DTCs) and/or affect proper operation.

The following items can affect the electrical connections:

Bent pins in the connector from rough handling during connection and disconnection.
Wires backing away from the pins or coming un-clamped (in either internal or external wiring harness).
Dirt contamination entering the connector when disconnected.
Pins in the internal wiring connector backing out of the connector or pushed out during reconnection.
Excessive transaxle fluid leaking into the connector, wicking up into the external wiring harness, and degrading the wire insulation.
Water/moisture intrusion in the connector.
Low pin retention in the external connector from excessive connection and disconnection of the wiring connector assembly.
Pin corrosion from contamination.
Broken/cracked connector assembly.
Points to remember when working with transaxle wiring connector assembly.
To remove the connector, squeeze the two tabs towards each other and pull straight up (refer to illustration).

Carefully limit twisting or wiggling the connector during removal. Bent pins can occur.

DO NOT pry the connector off with a screwdriver or other tool.

To reinstall the external wiring connector, first orient the pins by lining up arrows on each half of the connector.

Push the connector straight down into the transaxle without twisting or angling the mating parts.

The connector should click into place with a positive fell and/or noise.

Transaxle control module (TCM)

The transaxle control module (TCM) is an electronic device which monitors inputs to control various transaxle functions including shift quality and transaxle sensors, switches, and components to process for use within its' control program. Based on this input information, the TCM controls various transaxle output functions and devices.

Data link connector (DLC)

The data link connector (DLC) is a multiple cavity connector. The DLC provides the means to access serial data from the TCM to aid in powertrain diagnosis. The DLC allows the technician to use a scan tool to monitor various systems and display diagnostic trouble codes (DTCs). The DLC connector is located within the driver's compartment, directly below the steering column.

Explain of the data link Connector (CAN TYPE) 2.0L DOHC (Delphi 32 bit)

.	A connector (blue)	B connector (green)	C connector (gray)
1	Solenoid 2	Fluid Temperature Ground	Selector Lever Line L1
2	Power Mode Indicator /Auto Transaxle Emergency Lamp	Input Speed Sensor (+)	Not Used
3	EDS 4	BAT +	Not Used
4	TFT Sensor	Input Speed Sensor (-)	Hold Mode Switch
5	Brake Switch	Output Speed Sensor (-)	Not Used
6	Hold Mode Indicator	Selector Lever Line L3	EDS Supply
7	Diagnose(DLC)	Input Speed Sensor Ground	EDS Supply
8	Can High	Tachometer	Solenoid Supply
9	Solenoid 1	Power Mode Switch	Not Used
10	Pressure Control Solenoid Valve(EDS 5)	Output Speed Sensor (+)	Not Used
11	Pressure Control Solenoid Valve(EDS 3)	Selector Lever Line L4	Not Used
12	Pressure Control Solenoid Valve(EDS 6)	Ground	Not Used
13	Not Used	Ground	PNP Signal (TCM→ECU)
14	Not Used	Not Used	Not Used
15	Not Used	Selector Lever Line L2	IG ON
16	Can Low	Not Used	IG ON

TCM INPUTS THAT AFFECT THE 4HP 16 TRANSAXLE

Throttle position sensor

Provides throttle position data to the TCM for determining shift patterns and LOC apply/release.
An incorrect throttle position sensor input could causes erratic or shift pattern, poor shift quality or LOC function

Automatic Transaxle Output (Shaft) Speed Sensor

Provides vehicle speed data to the TCM for determining shift patterns and LOC apply/release, and gear ratio calculations.
An incorrect A/T OSS input could causes erratic or shift pattern, poor shift quality or LOC function.

Automatic Transaxle Input (Shaft) Speed Sensor

Provides transaxle input speed data to the TCM for determining shift patterns and LOC apply/release, and gear ratio.

Engine Coolant Temperature Sensor

Provides coolant temperature data to the TCM for determining initial LOC engagement.
An incorrect engine coolant temperature sensor input could causes an incorrect initial LOC apply

Engine Speed

The ignition module provides engine speed data to the TCM.
The TCM uses engine speed information for controlling wide open throttle shifts and the LOC PWM solenoid duty cycle.

Brake Switch

Provides brake apply information to the TCM for controlling LOC apply and release.
An incorrect LOC brake switch input could causes an incorrect LOC apply or release.

Transaxle Fluid Temperature (TFT) Sensor

Provides transaxle fluid temperature information to the TCM for determining alternate shift patterns and LOC apply during high temperature conditions (hot mode operation).
An incorrect transaxle temperature sensor input could causes altered shift patterns, poor shift quality and incorrect LOC apply.

COMPONENT LOCATOR

TRANSAXLE IDENTIFICATION INFORMAITON