Performance Controls: Notes

Fig 1: Performance Controls Unit

Engine Speed Signal (TD): is produced by the ECM as an output function. The TD signal is a processed square wave signal that indicates engine RPM. The signal is made available to other control modules including the Instrument Cluster, EWS and the 20 pin Diagnostic Socket.

The TD output is a square wave modulated signal. The frequency of the signal is directly proportional to RPM. The receiving control module detects RPM by the number of pulses.

Load Signal (Ti): is produced by the ECM as an output function that represents the actual amount of fuel injected. It is made available to other control modules as an input for operation. These control modules include:

OBC=Fuel consumption for MPG and Range.
Instrument Cluster = MPG Gauge
EGS = Load signal for shift points (If Equipped)

The Ti output is a processed square wave signal. The frequency of the signal is proportional to engine RPM. The pulse width and duty cycle will vary to reflect the injection quantity.

Fig 2: Identifying Engine Speed Signal (TD)

Engine Speed (TR) for EGS: is an additional variation of the engine speed signal. The "TR" signal is produced ECM as an additional output function. Like TD, "TR" is a processed signal that indicates engine RPM for the EGS (if equipped) to determine shift points.

The TR signal is a pulse wave signal. The frequency of the signal directly proportional to RPM. The signal is overlapped on the fuel pump relay control signal from the ECM.

Fig 3: Identifying Engine Speed (TR) For EGS

Throttle Position (DKV) for EGS: is the output signal to the EGS Control Module (if equipped). The DKV signal is a pulse width modulated signal directly proportional to the linear throttle position sensor input signal.

This output signal is used by the EGS Control Module for determining shift points.

Fig 4: Identifying Throttle Position (DKV) For EGS

EGS Ignition Timing Intervention Signal: The ECM receives an input signal from the EGS Control Module (if equipped) that will retard the ignition timing. This is a momentary ground signal from the EGS during a gear change to reduce engine torque for smoother shifts.

The EGS releases the ground so the ECM will resume ignition timing advance at the completion of the "shift".

Fig 5: Identifying EGS Ignition Timing Intervention Signal

A/C Compressor Control: is an output of the ECM. The ECM controls the A/C Compressor Relay based on signals from the IHKA/IHKR Control Modules.

When the driver selects the "snow flake" button, the IHKA/IHKR Control Module signals the ECM (AC) which "arms" it for compressor activation.

The ECM prepares for the additional load of the compressor by modifying the ignition timing and stabilizing idle speed.

When A/C compressor activation is required the IHKA/IHKS signals the ECM through the high/low refrigerant pressure switches (KO). The ECM will provide a ground circuit for the A/C Compressor Relay.

The A/C Compressor Relay is deactivated during wide open throttle acceleration at low speeds to allow the engine to quickly achieve maximum power.

Fig 6: Identifying A/C Compressor Control Circuit

Driveaway Protection System Interface EWS I (1-94 thru 12-94 production): was added to all vehicles in January 1994. It is controlled by the Central Locking System of ZKE and by the On-Board Computer code function (if equipped).

The Starter Immobilization Relay is activated when:

The vehicle is locked from the outside (Central Locking - GM output to Relay).
The On-Board Code function is set.

An activated relay performs two functions to deter vehicle theft:

Ignition and Injection functions of DME are disabled (switched high output signal.)
The KL 50 start signal circuit is opened to prevent starter operation.

Fig 7: Identifying Driveaway Protection System Interface EWS I

Driveaway Protection System Interface EWS II (from 1-95 production): and ECM Control Modules are synchronized through an individual serial number (ISN). The ISN is a unique code number that is permanently assigned to the ECM and also stored in the EWS II Control Module. The ISN must match every time the ignition is switched "ON", before the ECM drive away protection feature will be cancelled.

Engine Control Modules designed to operate with the EWS II system will not interchange with ECMs from previous models.
The ISN replaces the BC Code input to the ECM.
The ISN is unique to each ECM and cannot be changed or overwritten. The ISN is transferred / stored in the EWS II Control Module using the DIS/MoDIC (including diagnosis).
Everything the ignition is switched "ON" the ISN number is sent from the EWS Control Module to the ECM, as a digital coded signal. The numbers must match before the ECM will release the driveaway protection.
The ISN is continuously sent to the ECM as long as the ignition is switched on (KL15).
The ECM will disregard the loss of the ISN after the engine is running.

Fig 8: Identifying Driveaway Protection System Interface EWS II