SECTION 2

GENERAL INFORMATION

1.0 Subject

General Information

2.0 Scope

This general information document provides information not suited to be included in any other section or information which would have to be included in a number of places.

3.0 GMP-4 Turbo Hardware

3.1 Inputs

3.1.1 Analog Inputs

3.1.1.1 Oxygen Sensor

The oxygen sensor signal is a voltage ranging from low level to high level as the air/fuel ratio ranges from lean to rich.

3.1.1.2 Coolant Temperature

The coolant temperature is sensed by a thermistor and is determined as a percentage of the A/D reference voltage.

3.1.1.3 Throttle Position

The throttle position sensor input is sensed by a potentiometer on the throttle shaft and determined a percent of the A/D reference voltage per a percent of full scale throttle travel.

3.1.1.4 Manifold Air Temperature (MAT)

The manifold air temperature is sensed by a thermistor and is determined as a percentage of the A/0 reference voltage (1K internal pull-up resistor).

3.1.1.5 Manifold Absolute Pressure (MAP)

The manifold pressure is sensed by an absolute pressure transducer, and is determined as a percentage of the A/D reference voltage.

3.1.1.6 Diagnostics/ALDL Input

This signal is used to select the mode of operation; normal, factory test, diagnostics or ALDL made.

3.1.1.7 Electronic Spark Control Knock Sensor

The Electronic Spark Control Knock Sensor input is sensed by a mechanical vibration sensitive sensor mounted on the engine and determined analog signal per noise enhancement.

3.1.2 Discrete Inputs

3.1.2.1 Park/Neutral (P/N)

The P/N input Is a switch to ground input, where a grounded input indicates P/N.

3.1.2.2 A/C High Head Pressure Switch (Fan Request)

This signal comes from a normally closed switch to ignition and signifies high A/C head pressure for use as a fan request. Fan is requested when this switch is open.

3.1.2.3 Power Steering Pressure Switch (PSPS*)

This signal comes from a normally open switch to ground and signifies high power steering pressure when closed (power steering cramped).

3.1.2.4 Air Conditioner Dash Switch (A/C)

This signal comes from a normally open switch to ignition which is closed when air conditioning is requested.

3.1.2.5 Exhaust Gas Re-circulation Control (EGR)

This signal comes from a normally open switch to ground and signifies to direct exhaust gases from the exhaust manifold into the intake manifold when closed.

3.1.3 Other Inputs

3.1.3.1 Engine RPM

Reference pulses input from the HEI module are used to compute engine RPM.

3.1.3.2 Vehicle Speed

3.1.3.2.1 Optical Speed Input

An optical Vehicle Speed Sensor (VSS) provides a signal which changes from low level to high level 2002 times per mile. The time between each of these pulses is used to compute vehicle speed in MPH.

3.1.3.2.2 Magnetic Speed Input

A magnetic Vehicle Speed Sensor (MVSSA, MVSSB) provides a signal which changes from low level to high level. The pulse range can be from 2002 pulses per mile to 28,624 pulses per mile. The time between each of these pulses is used to compute vehicle speed in MPH.

3.2 Outputs

3.2.1 EST/Bypass

These outputs are used in conjunction with the Computer Controlled Coil Ignition (CCCI) module or HEI module for the electronic spark timing algorithm.

3.2.2 Check Engine Light

This output is used to flag a malfunction within the system and to flash out malfunction codes or rich/lean status.

3.2.3 Idle Air Control Motor Outputs

Four outputs are provided to control movement (speed and direction) of the IAC stepper motor.

3.2.4 Injector Driver Output

One output line is provided to drive a single 1.25 ohm ramp and hold injector.

3.2.5 Solenoid Outputs

• • Torque Converter Clutch
  • Fan Control Relay
  • Air conditioner Clutch Relay/Air Switch
  • Wastegate
  • Electronic Vacuum Regulator Valve

3.2.6 Fuel Pump Relay Driver

3.2.7 Serial Data Output

The Serial Data Output driver is a unidirectional (output only) driver circuit for high-speed (3192 baud) data.

4.0 PFI Software

4.1 Coolant Temperature

Due to the nature of the transducer interface configuration and the characteristics of the temperature sensing thermistor, the A/D conversion is non-linear with coolant temperature. ROM tables *FCLT348* and *FCLT4K* linearize coolant temperature to provide a coolant range from -40 to +152 Deg C (3/4 of a degree per count).

4.1.1 Dual Coolant Temperature Pull-up Logic

Software has the capability to switch between a 348 ohm pull-up and a 3996 ohm pull-up if the system is not operation in back-up fuel. The software controlling this pull-up is described below.

• • Initialized to 3998 ohm pull-up on power-up
  • Switches to 348 ohm pull-up once temperature exceeds 50 Deg C and COP2 has been toggled for at least 100 msec.
  • Switches to 3998 ohm pull-up if temperature drops to or below 39.5 Deg C or software has stopped toggling COP2

4.2 Oxygen Sensor Input Voltage

The relationship between the oxygen sensor A/D value and the actual oxygen sensor input voltage is given by the following equation.

02AD = VIN * 1152/VREF = VIN * 225.88 (nominal)

Where: 02AD = Oxygen sensor voltage in A/D counts

VIN = Oxygen sensor voltage

VREF = A/D reference voltage (5.1 volts nominal)

This provides a usable range of oxygen sensor voltages from 0 to 1.1289V with a resolution of 4.427 mV when the reference voltage is 5.1V.

4.2.1 Filtered Oxygen Sensor (ADOZFILT)

Oxygen sensor voltage is filtered each 12.5 msec with *KAOOZAF* specifying the filter coefficient. The filtered value of oxygen sensor is initialized to *K02FFO* whenever the engine is not running or a system initialization occurs.

4.2.2 Slow Trim Filtered Oxygen Sensor (AOO2AFSC)

AOO2AFSC is a version of AOO2A used in the fuel logic. *KFILTOZS* is the filter constant. For initialization, ADO2FSC is set equal to *KO2FFO*. For conditions when the fuel integrator is reset, AOOZAFSC is set equal to *KCLOXTH*.

4.3 Throttle Position Load (NTPSLD) Calculation

NTPSLD = (*K3*) * (ADTHROT - ADTAOFF)

Where: *K3* = Gain Calibration

ADTHROT = Throttle Position in AID Counts

ADTAOFF = Filtered 'lower' TPS Readings

4.3.1 Lower TPS Filtering for TPS Offset

ADTHROT Is filtered at a 12.5 msec rate when the current value of AOTHROT is less than or equal to the current filtered value of TPS. AOTAOFF is initialized to a value of *K4* and *KTAOFF* specifies the filter coefficient.

4.3.2 Throttle Position for Use in Calculating Delta TPS

Filtered values of throttle position are maintained for DE and AE calculations (see Fuel Section). They are called Transient Fuel Filtered Variables. Filter coefficients are selected from the following table. The "hot" coefficients are used when the coolant temperature exceeds *KTFFTT* and *KAFOPTL*, bit 4 = 1. If *KAFOPTZ*, bit 4 = 1, manifold air temperature is used. The "hot" manifold air temperature threshold is *KTFFTTM*.

Filtered Filter Coefficient

Variable Cold Hot

AE TPS TFTAAV KFILTTAC KFILTTAH

DE TPS TFTAAVDE KFIDETAC KFIDETAH

4.4 Engine Speed (RPM)

Engine RPM is computed from the time between the distributor reference pulses per the following equation:

RPM = 12O/(CYL * TREF)

Where: RPM = Engine speed in RPM

TREF = Time interval between the falling edge of the last two reference pulses

CYL = Number of Cylinders

Number of Cylinders *KNUMCYL*

3 96 ($60)

4 128 ($80)

6 192 ($C0)

8 0 ($00)

4.4.1 Filtered RPM

RPM is filtered each 12.5 msec with *KRPMFILT* specifying the filter coefficient.

4.4.2 NTREY65

NTREV65 represents the period of 90 degrees of engine revolution. Its value is obtained from a counter which is triggered from reference pulses. The transfer function is given.

NTREV65 = (15 * 2^16)/RPM

where: T = reference period in seconds

REF = 216 * TREF

4.4.3 NTRPMX

Engine speed variable NTRPMX is calculated in inverse proportion to the reference period.

NTRPMX = (155.6 * 256)/NTREV65

= RPM/25

4.5 Vehicle Speed (MPH)

The vehicle speed sensor generates 2002 pulses per mile. This corresponds to a frequency of 0.556 pulses per second per MPH. The minimum detectable vehicle speed is that which corresponds to a pulse to pulse interval of 1 second or 1.798 MPH. If no pulse is received within a 1 second interval, the speed will be considered as 0 MPH.

The vehicle speed variable most commonly used in the software is NMPH.

NMPH = (16/5) * FILTMPH

Where: NMPH = Normalized miles per hour

FILTMPH = Filtered miles per hour (see software filtering technique)

NMPH is limited to 224 which corresponds to 70 MPH.

4.5.1 Filtered Vehicle Speed

Vehicle speed is filtered each 5Oms with *KFILTMPH* specifying the filter coefficient.

4.7 Software Filtering Technique

Various input signals and software variables are conditioned by a software first order lag filter. Some of these signals and oxygen sensor voltage, vehicle speed, and manifold vacuum pressure. The filter can be expressed as follows:

FX1 = FXO + (I - FXO) * K

Where: FX2 = New filtered value

FXO = Old filtered value

I = Current unfiltered input value

K = Filter coefficient (0 to .996)

or FX1 = FXO + (I-FXO)*N

256

- FXO + (I-FXO)*256*K

256

= FXO + (I-FXO)*256*(1-e**(-T/t))

256

Where: N = Filter coefficient value in computer units

= 256*K

= 256(1-e**(-T/t))

T = Software loop time (update rate) in seconds

t = Filter time constant in seconds

- -T/In(1-(N/256))

NOTE: The filter coefficient should not be set to 0. This will result in the output of the filter being forced to 0.

4.8 Table Lookup

The software has the capability to interpolate between points for purposes of two and three dimensional table lookups. If the value of an X or Y parameter exceeds the range of the tables, the nearest endpoint will be selected.

4.9 Diagnostic Checksum

For purposes of testing the integrity of non-volatile memory a rotate and add incrementing checksum is applied to the malfunction flag words.

4.9.1 Non-Volatile RAM Failure

The non-volatile RAM is indicated as failed if any of the following conditions are satisfied.

• • Initialization checksum (double byte) of the five malfunction flag words does not agree with the value last calculated.

The above condition will result in the block learn memory cells being set to 128, the present IAC motor position being set to *KISSWNA* + *KISPKDL*, the following IAC terms being set as follows:

ISWNAC = *KISSWNA*

ISWWAC = *KISSWNA* + *KACDLD*

ISWWAC (park) = *KISSWNA*

ISWWAC (park) = *KISSWNA* + *KACOLD*

The rest of non-volatile memory is cleared.

• • BLM contents greater than *KBLMMAX* or less than *KBLMMIN* (checked each 50 msec during block learn).
  • This condition will result in the block learn memorv cells being set to 128.

4.10 High Voltage Disable of ECM Outputs

If ignition voltage is greater than or equal to 16.9 volts all PWM and discrete outputs will be disabled except for the check-engine light output.

4.11 Computation Rates

4.11.1 6.25 Msec Logic

4.11.2 12.5 Msec Logic

4.11.3 50 Msec Logic

4.11.4 100 Msec Logic

4.11.5 100 Msec Logic

4.11.6 RAM Refresh

RAM is refreshed during the dead time while waiting for the next real time interrupt to occur. Bench testing will insure that all of RAM is refreshed at least nnce every 100 msec.

5.0 Instrumentation Module (IM) Information

Two possible Heads-up Display (HUD) configurations are selectable utilizing the CAL A/B switch on the HUD unit.

5.1 Display "A'" (Cal A) Selector Switch Information

Display ""A"' Selector Switch (Upper and Lower) Positions

0 1

9 2

8 3

7 4

6 5

5.1.1 Upper Switch Position Display Function Table

Position Display Parameter Label

0 Spark Advance (Degrees) SATDC

1 Barometric Pressure (kPa) ADBARO

2 Engine Coolant Temperature (Degrees C) COOLDEG

3 Manifold Air Temperature (Degrees C) MATDEG

4 IAC Present Motor Position (Steps) ISSPMP

5 Data Change Slew Value IDATAMOD

6 RAM Address Slew Value IADDRMOD

7 Vehicle Read Speed (KPH) FILTMPH

8 A/F or Base Pulse Change Slew Value IAFMOD

9 Block Learn Multiplier BLM

5.1.2 Lower Switch Position Display Function Table

Position Display Parameter Label

0 Spark Advance Change-Slew Value ISPKMOD

1 Knock Spark Retard NOCKRTD

2 Closed Loop Integrator Value INT

3 Wastegate Duty Cycle (Percent) WGATEDC

4 IAC Desired Motor Position (Steps) IMPMOD

5 Base Pulse Width (Msec) BPW

6 Contents of RAM Location CONTENTS

7 Throttle Angle (Percent) NTPSLD

8 A/F Ratio AIRFUEL

9 EGR Duty Cycle (Percent) EGRDC

 

5.2 Discrete Status Word Display Information (Display "A")

Discrete Display of Status Word

Status #1

NVM BLM BKR TCC FAN AC PFM Acc

S7 S6 S5 S4 S3 S2 S1 S0

Status #2

IAC ASYNCH LE AE DE PE CL R

5.2.1 Status Word #1 Display Information

Position Status Information

S7 Non-Volatile Memory Failure

S6 BLM Cell

S5 Burst Knock Retard

S4 TCC Enabled

S3 Fan ON

S2 Air Conditioning Request

SI Premium Fuel Mode

SO Air Conditioning Clutch Disabled

5.2.2 Status Word #2 Display Information

Position Status Information

S7 IAC Motor Moving

S6 Asynch Pulse Mode

S5 Learn Enabled

S4 Acceleration Enrichment

S3 Decel Enleanment

S2 Power Enrichment

S1 Closed Loop Enabled

SO Oxygen Sensor RICH

5.3 Display "B" (Cal B) Selector Switch Information

Display "B'. Selector Switch (Upper and Lower) Positions

0 1

9 2

8 3

7 4

5 5

5.3.1 Upper Switch Position Display Function Table

Position Display Parameter Label

0 Average MPG MPGMEAN

1 Power Steering Stall ISALPA

2 Cold Control IAC Bias for P/N NBIASPN

3 IAC Drive Motor Position, Warm With No A/C ISWNAC

4 Manifold Absolute Pressure MAPP

5 IAC Drive MQtOr Position, Warm With A/C ISWWAC

6 Filtered RPM ISES

7 Battery Voltage ADBAT

8 FAN On Time FAN

9 Filtered O2 Value (A/D Counts) ADO2AFSC

5.3.2 Lower Switch Position Display Function Table

Position Display Parameter Label

0 IAC Extended Throttle Cracker With No A/C ETCACOFF

1 Coolant Offset for IAC ISMPTV

2 Cold Control IAC Bias For Drive NBIASDR

3 IAC P/N Motor Position, Warm With No A/C ISWNACP

4 IAC Desired Motor Position ISDSMP

5 IAC P/N Motor Position, Warm With A/C ISWWACP

6 Desired Engine Speed (RPM) DESSPD

7 Instantaneous MPG MPG

8 Delay Counter For P/S Crack Decay PSTCLC

9 IAC Extended Throttle Cracker With A/C ETCACON

5.6 Analog Channel Assignments (Continued)

Min. Max.

Block Parameter Scale Scale

14 IAC OMP Slew Value 0 Counts 255 Counts

15 Base Pulse Width 0 mSec 0 mSec

16 IMMW3 (Octal) -- --

17 TPS Load 0% 100%

18 Air/Fuel Ratio 0 A/F 25.5 A/F

19 Battery Voltage 0V 25.5V

20 IMMW1 0V 25.5V

21 IMMW2

22 RPM 0 RPM 6400 RPM

23 Manifold Absolute Pressure 10.35KPa 104.4KPa

24 Closed Loop Correction --

25 IAC Present Motor Position

26 Not Used

27 Not Used

28 Not Used

29 Not Used

30 vehicle Road Speed (MPH) 0 KPH 200 KPH

31 Base Pulse Width 0 msec 100 msec

32 IMMW1B

33 IMMW28

34 RPM 0 RPM 3200 RPM

35 RPM (Filtered) 0 RPM 1600 RPM

36 Base Pulse Width 0 msec 200 msec

37 IAC Present Motor Position 0 Counts 200 Counts

38 Manifold Air Temperature -40 Deg 152 Deg

39 A.E. Delta MAP 0 kPa 100 kPa

40 A.E. Delta Throttle 0% 100%

41 D.E. Delta MAP 0 kPa 100 kPa

42 D.E. Delta Throttle 0% 100%

43 N/V Ratio for Shift Light 0 Ratio 144 RA

44-100 Not Used