Electronic Transmission Control: Other BMW 3 series E36

FUNCTIONAL REQUIREMENTS

The control unit sends the shift pulses for upshifts and downshifts to the transmission control unit (solenoid valves, modulation pressure) and decides upon the corresponding torque converter clutch engagement, taking comfort and safety into consideration. For this purpose, it processes in a computer program the input variables such as engine speed, output speed, injection signal, throttle (accelerator pedal) position, kick-down switch, drive program, selector lever position, A/C compressor and oil sump temperature.

CONVERTER LOCKUP CLUTCH CONTROL

The converter lockup clutch (WK) is activated dependent upon the accelerator pedal position, transmission output speed, drive program as well as the engaged gear (only in 3rd and 4th gear). The converter lockup clutch opens in coasting mode. After starting the engine, it is not possible to engage the converter lockup clutch by way of temperature-dependent activation.

ADAPTIVE GEARSHIFT CHARACTERISTIC CONTROL

When pulling a trailer or driving on steep gradients, the changed acceleration capacity of the vehicle is evaluated by the control units. For this purpose, the control unit selects (adapts) suitable gearshift programs to avoid pedal shifts. The changed gearshift points are intentional and normal.

GEARSHIFT COMFORT CONTROL

The gearshift quality is controlled by way of the modulation pressure and the engine intervention function (torque reduction by retarding the ignition timing). The main pressure is constantly calculated by way of an algorithm with tuning-specific parameters (engine torque, differential speed [engine speed difference before and after shifting], output speed and constant pressure component). The signal A/C COMPRESSOR ON/OFF is supplied by the Digital Motor Electronics (DME). The engine torque characteristic map is corrected in order to avoid a loss of gearshift comfort when A/C compressor is switched on.

DRIVE PROGRAMS

The shift points for the "E" (Economy) and "S" (Sports) program as well as for kick-down are stored in the form of characteristic curves in the control unit. Selection can be made with the program switch between these programs and manual shifting. The program switch is designed as a push button connected with respect to ground. On the US version, 2 programs are selected via push button (A/M). Assignment of the gears to the selector lever position in the manual drive program

1. Position: D, 3, 2, 1
2. Gear: 3, 3, 2, 1 Characteristic curves in position "D" based on consumption and comfort. Characteristic curves in position "3" and "2" based on performance.

Special Features

To ensure the engine reaches its operating temperature as fast as possible, the transmission shifts on the basis of the performance-orientated characteristic curves of the S-program in accordance with the following criteria.

1. New start with transmission oil temperature less than 140°F (60°C).
2. Time span maximum 195 seconds.
3. Up to maximum 37 MPH.

Drive Program Indication

The drive program is indicated in the program button in that the selected letter is highlighted in the button.

Note. The drive programs cannot be switched over by the EGS control unit before engine start since the control unit can only complete its initialization phase after it has detected an engine speed.

SAFETY FUNCTIONS

By way of plausibility checks and checking the line connections for shorts or opens, the control unit can detect and store defects.

In the event of failure of the transmission control or when defects are detected which lead to critical driving situations (for example: impermissible downshift), the mechanical emergency program is activated (transmission control unit is switched off and failure indicator activated.) A self-test of the entire safety hardware takes place during each new start.

The vehicle can only be driven with restrictions in the mechanical emergency program (only the 3rd, 4th gears and reverse can be shifted.) In this case, 3rd gear is engaged in selector lever position "2" and "1", 4th gear in position "0" and "3" and reverse in position "R". The main pressure assumes its maximum value. Reverse lock and shift-lock, if installed, of the selector lever are not active.

Note. Downshifts engaged manually at a speed which is too high are generally not performed.

The R-lock (reverse lock-out) prevents reverse being shifted hydraulically at a speed above approximately 5 MPH.

SHIFT-LOCK

It is only possible to shift out of the positions "P" or "N" after evaluation of following signals

1. Brake.
2. Road speed.
3. Engine speed.
4. Time.

The selector lever is locked when no brake signal is detected with the engine running and the vehicle stationary. A time delay function of approximately 0.5 second is used for operation under winter conditions. Brake switch is designed as a normally open contact referred to 12 volts and the brake light test switch as a normally closed contact referred to ground. Shift lever is locked by way of a solenoid on the selector lever switch.

FAULT INDICATION WITH SERIAL DATA TRANSFER

Transmission control unit transfers data on the fault indicator line (pin No. 29) relating to the transmission oil temperature and the selector lever coding (4th or 5th gear) to the instrument cluster. The fault light is activated by the instrument cluster when a voltage of 12 volts is applied on this line for longer than one second. This is the case when the EGS control unit is still in its initialization phase (ignition on, engine still not started), or in the emergency program or when the wire has an open (pull-up resistor in instrument cluster).

Conditions For Component Activation

1. Data transfer okay.
2. Selector lever in position P or N.
3. Output speed less than 300 RPM.
4. If the message "current defect detected and stored" is indicated, first print out the contents of the defect code memory then clear the defect code memory and repeat component activation.

Type Of Defect

Indicated here is whether the defect is an open, a short to voltage, a short to ground or a plausibility error.

Defect Currently Set

The response of the control unit to this statement can be in the affirmative, negative or conditionally affirmative or conditionally negative. In the case of a restricted reply to the question as to whether the defect code is currently set, the additional information STATEMENT NOT SURE SINCE TEST CONDITION IS NOT CURRENTLY FULFILLED appears. This means that the control unit cannot currently check the indicated defect code since, for example, the component is not active. However, the defect code was set or not set the last time the test condition was fulfilled.

Intermittent Defect

The reply to this statement is in the affirmative when the defect disappeared at least once and then reappeared. Intermittent defect codes additionally indicate how often the defect disappeared and reappeared.

Defect Detected

Here additional information is given on the operating conditions, under which the defect was detected for the first time

1. Output speed.
2. Engine speed.
3. Oil temperature.
4. Battery voltage.
5. Pressure regulator current.
6. Selector lever position conductor L1 to L4.
7. Transmission.
8. Throttle angle, accelerator pedal position.
9. Kick-down active yes/no.
10. A/C compressor.
11. Engine intervention.
12. Solenoid valves.

Explanation

The lifting solenoid P/N shift-lock is checked completely by the control unit during the initialization phase by temporarily activating it. The following defects can be detected during operation depending on the condition of the lifting solenoid

1. Active: Short to ground, plausibility (driver transistor defective).
2. Passive: Short to voltage, open.

Effect Of Defect

Mechanical emergency program.

Possible Cause

Wire or winding of the lifting solenoid defective, or driver transistor defective.

This defect code is stored when 2 or 3 of the wires to the control unit pin No. 2 (E-program), No. 31 (M-program), No. 34 (S-program) are applied simultaneously to ground. Consequently, program switchover is not possible.

Control unit sets E-program.

Wires from program button to EGS control unit defective or program button defective.

This defect code is stored when the wire from the control unit pin No. 4 has an open or is applied to ground for longer than 3 seconds. If wire is applied to ground, this defect code is also stored in DME control unit.

Ignition timing can no longer be retarded by the DME control unit and consequently the torque is no longer reduced during gearshift. To protect the clutches from excessively long slip times, gearshifts are only carried out at maximum pressure at an earlier point (i.e. earlier upshift).

Wire defective.

There is a defect if no or 100 percent KVA signal (ti signal) is detected at an engine speed between approximately 1000 RPM and 5000 RPM and at an accelerator pedal position between approximately 35 percent and 70 percent.

Wire to pin No. 9 or injection signal from DME defective.

Defect code is stored when control unit receives no engine speed signal in a drive range (R, D, 3, 2, 1) at an accelerator pedal position greater than 12 percent and an output speed greater than approximately 1000 RPM. Control unit can differentiate between the following types of defect

1. Open or short to ground.
2. Short to voltage.

Mechanical emergency program.

Wires defective.

This defect code is stored when the control unit receives no output speed signal at an engine speed above approximately 3000 RPM in a drive stage (R, D, 3, 2, 1).

Mechanical emergency program.

Wire from EGS control unit pin No. 14 and Pin No. 20 to speed sensor, speed sensor, torque converter or clutches defective.

For this defect code, the control unit can differentiate between 3 different types of defect

1. Open or short to voltage (minimum temperature).
2. Short to ground (maximum temperature).
3. Transmission temperature higher than 329°F (165°C).

A substitute value of 212°F (100°C) is used. Transmission oil has overheated or aged prematurely. It is recommended to change the transmission oil.

Wire from control unit pin No. 17 and pin No. 22 to oil sump temperature sensor defective, or oil sump temperature sensor (soldered in wire harness of gearshift unit) is defective, or transmission overloaded.

This defect code is stored when the engine can be started although voltage is not applied at pin No. 26 (conductor 2, only active in position "P" or "N").

Open in lines or start interlock relay defective.

This defect code is stored when permanent voltage supply of control unit is interrupted.

Diagnostic information is lost (any stored defect codes are cleared from the control unit).

Wire open.

This defect code is stored when the kick-down signal does not agree with the signal of the accelerator pedal position.

The control unit suppresses kick-down detection.

Wire has short to ground or switch is defective.

Code is stored when voltage value is outside valid range (9-16 volts).

Voltage supply defective.

Solenoid valve for converter clutch is checked completely by control unit during the initial phase by briefly activating it. The following defects can be detected during operation depending on the status of solenoid valve

1. Active: short to ground, plausibility (driver transistor defective).
2. Passive: short to voltage, open.

Mechanical emergency program.

Wire or winding of solenoid valve WK defective, or driver transistor defective.

Pressure regulator is checked completely by control unit during the initialization phase by briefly activating it. During operation, the defect is detected by internal feedback of the signal.

Mechanical emergency program.

Wire or winding of pressure regulator defective.

Solenoid valve 2 is checked completely by the control unit during the initialization phase by briefly activating it. The following defects can be detected during operation dependent on the status of solenoid valve

1. Active: short to ground, plausibility (driver transistor defective).
2. Passive: short to voltage, open.

Mechanical emergency program.

Wire or winding of solenoid valve 2 defective, or driver transistor defective.

Solenoid valve brake band is checked completely by the control unit during the initialization phase by briefly activating it. The following defects can be detected during operation depending on the status of solenoid valve

1. Active: short to ground, plausibility (driver transistor defective).
2. Passive: short to voltage, open.

Mechanical emergency program.

Wire or winding of solenoid band defective, or driver transistor defective.

Explanation: The solenoid valve 1 is checked completely by the control unit during the initialization phase by briefly activating it. The following defects can be detected during operation dependent on the status of solenoid valve

1. Active: short to ground, plausibility (driver transistor defective).
2. Passive: short to voltage, open.

Mechanical emergency program.

Wire or winding of solenoid valve 1 defective, or driver transistor defective.

This defect code is stored when it is not possible to connect or disconnect ground for solenoid valves.

Mechanical emergency program.

Wire or ground supply to pin No. 54 defective.

This defect code is stored when the EGS control unit receives no signal or a defined defect signal (duty factor 4 percent) from the DME control unit relating to the throttle angle. Throttle signal is pulse width modulated and is always monitored completely by the control unit. The control unit can differentiate between the following types of defect

1. Open or short to voltage.
2. Short to ground.
3. Throttle defect detected by DME control unit.

A substitute value of approximately 15 percent accelerator pedal position is used (EGS control unit shifts up at a much earlier point).

Wire from DME control unit to EGS control unit pin No. 55 is defective or wires from throttle potentiometer to DME control unit are defective.

This defect code is stored when the speed ratio (n-ab) to (n-mot) for the current gear is outside the permissible slip tolerance. Monitoring is only effective at engine speeds greater than 3500 RPM.

Mechanical emergency program.

Electrically selected gear and hydraulically engaged gear do not agree. Disturbances in hydraulic shift unit. Solenoid valves connected incorrectly.

This defect code is stored when the engine speed for the downshift to be performed by the control unit is too great.

Mechanical emergency program.

Faults on TR signal line. Defect in EGS control unit.

This defect code is stored when the engine speed is too great in 1st or 2nd gear.

Mechanical emergency program.

Vehicle was accelerated (towed) in manually engaged 1st or 2nd gear to such an extent that the engine speed was 300 RPM above the limit speed.

This defect code is stored when a change has taken place in the EPROM.

Mechanical emergency program.

EPROM defective.

This defect code is stored when the DME control unit detects a defective temperature sensor. The DME signals this defect to the EGS control unit by sending a pulse modulated signal with a duty factor of 4 percent at a frequency of approximately 200 Hz on the DKT line.

Mechanical emergency program.

Engine temperature sensor or its wires to the DME control unit defective.

This defect code is stored when the DME control unit detects a faulty throttle signal. The DME control unit signals this defect to the EGS control unit by sending a pulse width modulated signal with a duty factor of 4 percent at a frequency of approximately 100 Hz on the DKT line.

Mechanical emergency program.

Throttle potentiometer or its wires to the DME control unit defective.

No kick-down shifts are performed.

KD switch defective or wire from KD switch to control unit pin No. 2 has an open or a short to voltage.

S-program cannot be switched.

Wire from program button to pin No. 34 at EGS control unit has an open.

M-program cannot be switched

Wire from program button to pin No. 31 at EGS control unit has an open.

Program switch over is not possible-only E-program (E36), or economy program is running but S-program is indicated in instrument clutster (E34).

No ground at program button-program button defective (E36), or wire from control unit pin No. 10 has an open or short to voltage (E34).

Torque is not reduced by retarding ignition during gearshift procedure. This results in longer slip times and premature wear of the clutches.

The wire from the EGS control unit pin No. 4 has a short to voltage.

Manual program is running but S-program is indicated in instrument cluster.

Wire from control unit pin No. 12 has an open or has a short to voltage.

Alternate gearshifts can occur when the air conditioning system is activated.

The wire from pin No. 21 at the control unit is defective.

Program switchover is not possible. Only E-program.

No ground applied at program button. Program button defective.

The selector lever cannot be engaged in a drive range despite the brake pedal being depressed. (Only with PIN shift-lock).

The wire at control unit pin No. 39 and pin No. 15 is defective.

No torque reduction due to retarded ignition during gearshift. This results in long slip times and premature wear of the clutches.

Wire from control unit pin No. 4 has a short to voltage.

Transmission fault lamp lights in the instrument cluster despite the transmission operating normally.

The wire from control unit pin No. 29 to the instrument cluster has an open or a short to voltage.

The air conditioning system can constantly switch on and off when active.

Wire from control unit pin No. 21 defective.

Despite the brake pedal being pressed, the selector lever cannot be engaged in a drive position. (Only in GS 4.14 with PIN shift-lock).

Wire at control unit pin No. 39 is defective.

Although the transmission is operating normally, the message "transmission" appears in the instrument cluster.

Wire from control unit pin No. 29 to instrument cluster has an open or a short to voltage.

Diagnostic link TxD or RxD has an open or has a short to voltage or ground. The TxD link leads from the diagnostic socket pin No. 20 to the EGS control unit pin No. 13 and is bypassed to ground when the cover of the diagnostic socket is closed. The RxD links leads from the diagnostic socket pin No. 15 to EGS control unit pin No. 25 and is bypassed to terminal No. 30 when the cover of the diagnostic socket is closed.

The power supply to the EGS control unit pin No. 37 is interrupted.

COMPONENT TESTS

Note. Before disconnecting the control unit or the battery, use BMW tester and read out the defect code memory and print out with troubleshooting. Detach control unit connector only when the ignition is off. Check wires only with the control unit connector or component connector detached.

GEAR SELECTOR LEVER SWITCH

Check the gear selector lever switch by means of the universal adapter with the control unit connected and ignition switched on. Measure between Pin 1 (-) and the specified pins. "0" corresponds to approximately zero volt, "1" corresponds to approximately 12 volts. If a voltage is not measured at any position, check voltage supply of the selector lever switch. If activation is defective, remove and check selector lever switch. See GEAR SELECTOR LEVER SWITCH CHECK (3-SERIES E36) or GEAR SELECTOR LEVER SWITCH CHECK (5-SERIES E34) table. (Scheme 104) Replace lever switch as necessary. If okay, replace wires or plug connections. The back-up light is switched via pins RF and RF+ in selector lever position R.

Scheme 104

GEAR SELECTOR LEVER SWITCH CHECK (3-SERIES E36) (1)

GEAR SELECTOR LEVER SWITCH CHECK (5-SERIES E34) (1)

KICK-DOWN SWITCH

Check kick-down switch by means of the universal adapter and BMW service tester with the ignition switched on and control unit connected. Connect voltmeter between pin No. 30 (+) and pin No. 19 (-). See WIRING DIAGRAMS . With switch operating, less than one volt should be present. With switch not operating, greater than 10 volts should be present. If values deviate, check wire as well as plug-and-socket connection from control unit to kick-down switch and repair if necessary. If okay, remove kick-down switch, check and repair if necessary.

OIL TEMPERATURE SENSOR

If the displayed oil temperature in BMW service tester status monitoring does not agree with the actual status, measure resistance of the oil temperature sensor with the control unit disconnected and ignition switched off. See OIL TEMPERATURE SENSOR CHECK table. If values deviate, check wire and plug-and-socket connection from control unit to transmission and repair if necessary. If okay, replace wire harness in transmission control unit.

OIL TEMPERATURE SENSOR CHECK

PROGRAM BUTTON

Check the program button with the aid of the universal adapter with the control unit connected and ignition switched on. Measure between pin No. 19 and the specified pins. (Scheme 105)Or (Scheme 106). Number "0" corresponds to approximately zero volt, and "1" corresponds to approximately 12 volts. If inputs in control unit are not plausible, check ground connection to program button (pin No. 5 on E36; pin No. 31 on E34) and repair if necessary. (Scheme 107)Or (Scheme 108). If okay, remove program button. Check in accordance with switch diagram and replace if necessary. If okay, check wire and plug connection. Repair as necessary. If okay, replace control unit.

Scheme 105

Scheme 106

Scheme 107

Scheme 108

SOLENOID VALVES & HYDRAULIC PRESSURE REGULATOR

Check resistances of solenoid valves and of the hydraulic pressure regulator by means of the universal adapter with the control unit disconnected and ignition switched off. See SOLENOID VALVES & HYDRAULIC PRESSURE REGULATOR CHECK table. If values deviate, repeat test at gearshift unit, if okay, repair wire. If not okay, remove gearshift unit and repair or replace solenoid valves or MV-DR.

SOLENOID VALVES & HYDRAULIC PRESSURE REGULATOR CHECK

SPEED SENSOR N-AB

If the displayed output speed in BMW service tester status monitoring does not agree with the actual status, measure the resistance of the DZF by means of the a universal adapter with the control unit disconnected and ignition switched off. See CONTROL UNIT SPEED SENSOR CHECK table. If value deviates, check wire as well as plug-and-socket connection from control unit to speed sensor and repair if necessary. (Scheme 109) If okay, repair or replace speed sensor.

CONTROL UNIT SPEED SENSOR CHECK

Scheme 109

PIN VOLTAGE CHARTS

For pin voltage information on 3-series (Scheme 110)- (Scheme 112). For pin voltage information on 5-series (Scheme 113)- (Scheme 115).

Scheme 110

Scheme 111

Scheme 112

Scheme 113

Scheme 114

Scheme 115

Scheme 116

Scheme 117

Scheme 118

Scheme 119

Scheme 120

Scheme 121

Scheme 122