Home/Jaguar/XKR/Jaguar XKR I (1998-2004)/Repair manual/Automatic Trans/Diagnosis & Testing: Other

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Wiring diagrams Section: Automatic Trans

Shift Interlock Systems - Wiring Diagrams

Removal & Installation

Transmission Cooling

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Diagnosis & Testing: Other Jaguar XKR I

Automatic Trans 25 illustrations ~1287 words

OBD-II SYSTEMS

California OBD-II applies to all gasoline engine vehicles up to 14,000 lbs. Gross Vehicle Weight Rating (GVWR) starting in the 1996 MY and all diesel engine vehicles up to 14,000 lbs. GVWR starting in the 1997 MY.

"Green States" are states in the Northeast that chose to adopt California emission regulations, starting in the 1998 MY. At this time, Massachusetts, New York, Vermont and Maine are Green States. Green States receive California-certified vehicles for passenger cars and light trucks up to 6,000 lbs. GVWR.

The National LEV program (NLEV) requires compliance with California OBD-II, including 0.020" evaporative system monitoring requirements. The NLEV program apply to passenger cars and light trucks up to 6,000 lbs. GVWR nation-wide from 2001 MY through 2003 MY.

Federal OBD applies to all gasoline engine vehicles up to 8,500 lbs. GVWR starting in the 1996 MY and all diesel engine vehicles up to 8,500 lbs. GVWR starting in the 1997 MY.

OBD-II system implementation and operation is described in the remainder of this document.

EMERGENCY RUNNING (ELECTRONIC LIMP-HOME MODE)

The TCM constantly monitors the transmission for faults. In the event of a problem the TCM will adopt the limp-home mode, in which the last gear shifted remains engaged, until P or N is selected. The modulating and shift pressures will increase to maximum and converter lock-up will be inhibited.

Following the selection of P or N, the only ratios available will be 2 (irrespective of forward ratio manual selection) and R.

With the vehicle at rest, the procedure to manually select is as follows

Select P.
Switch OFF the ignition.
Wait 10 seconds.
Start the engine.
Select R (reverse will be selected).
Select D (2 will be selected).

The limp-home mode will be retained until the fault is remedied or the fault code has been erased. Cycling the ignition OFF/ON may clear intermittent faults. In certain cases the component may need to be operated before the fault code is cleared e.g. a shift solenoid.

EMERGENCY RUNNING (MECHANICAL/HYDRAULIC LIMP-HOME MODE)

Should slip be detected, due to a mechanical failure or loss of pressure, the transmission will either shift to, and hold 3 or shift to, and hold, the last gear which was known to be all right. This condition may be cleared by cycling the ignition OFF/ON following mechanical repair.

The operator will be made aware of certain faults by a warning message on the instrument cluster.

Data concerning OBDII related transmission failures is stored in the ECM for access via the J1962 socket.

SAFETY FUNCTIONS

These functions are designed to safeguard against inappropriate actions by the operator as well as system malfunctions.

The electrical and diagnostic system has been designed such that system integrity is protected at all times, the safety concept being based on the following three points.

The hydraulic system has "fail-safe" characteristics regarding its electrical operation, such that should the power supply be lost to the electro-hydraulic actuators the transmission will initiate a limp-home mode.
Recognition of critical shift operation by monitoring the last element in the signal path, i.e. the solenoid valve, and checking by means of redundant measured variables relative to engine, transmission and road speeds.
Each time the vehicle is started there is a check on the entire safety hardware and the associated program parts and signal paths. A malfunction in this part of the system, or triggering of the safety circuit, is communicated to the operator by a warning message on the instrument cluster.

Transmission Casing

The following components are housed within the casing

Stator, intermediate and output shafts.
Three epicyclic gear trains.
Six multi-disc clutch/brake packs.
Two freewheels (One-way clutches).
Hydraulic pump.
Parking lock assembly.
Electro-hydraulic control unit.
Internal harness and 13 pin connector with bayonet lock.

Power Flow Through The Transmission

From the Torque converter, power is transferred to the three epicyclic gear trains, various elements of which can either be joined together or held still by either the Freewheels or the Multi-disc Clutch/Brake assemblies (controlled by the Electro-hydraulic control unit). This combination of elements results in five forward and two reverse gear ratios. The resulting rotational torque is taken from the transmission output shaft, to the final drive assembly via the driveshaft

Hydraulic Pump

This engine driven pump is located at the front of the transmission casing and provides pressure for the hydraulic functions. The pump supplies fluid under pressure to the torque converter, gear train, electro-hydraulic control unit and the lubrication circuit. It also draws fluid from the fluid pan below the transmission casing, through a filter.

Parking Lock

This component prevents movement of the vehicle by engaging a fixed pawl with the parking lock gear located on the output shaft. The pawl is engaged by moving the gear selector lever to the park (P) position.

Electro-Hydraulic Control Unit

This unit, mounted in the transmission lower case, converts signals, mechanical from the J-gate and electrical from the TCM, into hydraulic functions. The following components are assembled to the unit

Selector valve.
Shift plate.
Control valve - modulating pressure.
Control valve - shift pressure.
Solenoid valve 1 <-> 2 and 4 <-> 5 shift.
Solenoid valve 3 <-> 4 shift.
Solenoid valve 2 <-> 3 shift.
Solenoid valve - converter lock-up.
Speed sensors (2).
Temperature sensor.

Speed Sensors

There are two speed sensors within the transmission assembly, which provide input to the TCM. These inputs, when used in conjunction with CAN data relative to engine speed (from ECM) and road speed (from ABS), are used to electronically control the transmission.

Temperature Sensor

The output from this sensor allows the TCM to compensate for the affect of fluid temperature on shift time and quality.

Shift Programs

Upon encountering the following conditions, the TCM will automatically use the Normal or Sports shift map to enhance the operation of the vehicle

Traction: When traction intervention is active.
Hot mode: Extreme engine/transmission temperatures.
Gradient: Under specific speeds and load.
Manual: Driver initiated override of the normal shift map when the LH side of the "J" gate is used.

Traction

When traction or stability control (engine or brake system derived) is operational the TCM will implement the traction map to maximize control of wheel slip.

Gradient

The gradient function is intended to enhance vehicle driveability when climbing a gradient or towing. The TCM will implement the function when increased driving resistance is detected, and provides enhanced driveability, additional cooling and/or increased performance as appropriate.

CONTROL MODULE PIN NUMBERING

The following table details the Pin numbering for the transmission control module.

Scheme 120

Scheme 120: CONTROL MODULE PIN NUMBERING

Scheme 121

ON-BOARD MONITORING

When the ignition switch is set to position II (ignition ON) the TML comes on briefly and then goes off again.

When the TCM detects a fault, it stores the fault code and activates the transmission fault-warning lamp (TWL). For faults detected in less critical inputs/outputs, the TCM substitutes the faulty input/output with a default value and continues the normal mode of operation. This allows the vehicle to be driven normally, although gear change quality will be affected.

CONTROL MODULE MALFUNCTIONS

The diagnostic detects malfunctions in the TCM ignition switched supply by measuring the system voltage. A fault is logged if the voltage is either too high or too low. The voltage is measured at the TCM.