A/c-Heater System - Automatic Oldsmobile Toronado Trofeo

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION

Note. The 1990 information in this article is from preliminary manufacturer sources. Final 1990 information was not available.

SYSTEM DESCRIPTION

The climate control automatic air conditioning system is of the cycling clutch orifice type. It is designed to cycle A/C compressor on and off to maintain desired cooling and to prevent evaporator icing.

Climate control system automatically controls vehicle interior temperature. Both heating and cooling systems are controlled by the Body Computer Module (BCM) by operation of mode doors and blower motor speed.

The standard control panel used for non-CRT system is the main control for all heating and air conditioning functions. (Scheme 1) The optional Cathode Ray Tube (CRT) operates the same as non-CRT system, except where noted. The CRT system is a pressure sensitive transparent film laid over viewing screen. In this film are sections, or key pads which are actually small switches.

The display and function of CRT can be changed from one system to another. These system function displays are known as pages. To make an operation change to climate control system, climate control page must be brought to CRT screen. (Scheme 2)

The other main components comprising the climate control system are: Electronic Control Module (ECM), programmer, power module, temperature sensors, Heat Vent Air Conditioning (HVAC) module and refrigeration system.

Scheme 1

Scheme 2

OPERATION

The climate control system automatically regulates and maintains selected in-car temperatures from maximum "COOL" 60°F (16°C) to maximum "HEAT" 90°F (32°C).

To select a new climate control mode or temperature level on CRT system, first bring climate control page to CRT screen. To make changes, press appropriate key pad on screen. (Scheme 2)

To select a different mode or temperature level on non-CRT system, press appropriate mode key pad and adjust temperature via "COOL WARM" key pad.

BODY COMPUTER MODULE (BCM)

The BCM is located behind glove box, next to programmer. The BCM contains a microprocessor which provides central control over all other components in climate control system. The BCM monitors system switches and sensors. Based on these inputs, along with program instructions within the computer memory, the BCM calculates proper outputs to operate climate control system.

BLOWER FAN CONTROL

Models with color CRT display have 3 manually selected blower speeds, or automatic operation when "AUTO" is selected.

Models with non-CRT display have 5 blower speeds that can be manually selected, or "AUTO" mode allows for automatic operation of blower fan.

On all models, the selected blower speed signal is sent from control panel via a serial data line to BCM. The BCM sends the blower speed signal to programmer, which amplifies the voltage signal and maintains a constant blower speed despite changes in system voltage. BCM monitors blower motor voltage feedback circuit and will increase or decrease signal voltage until proper blower speed is achieved.

MODE SETTINGS

Note. Modes identified within parentheses () refer to mode identification on CRT equipped vehicles.

"OFF" Mode

In this mode climate control system will not let blower motor or A/C compressor run, but system will still try to reach temperature selected by driver. Models with non-CRT will display outside air temperature when "OFF" is selected.

"AUTO" Mode

In this mode, all functions are controlled automatically. Temperature will adjust to setting and is maintained automatically through BCM operation of mode doors and blower speed.

"UPPER" Or ("UPPR") Mode

In this mode, air is distributed out A/C vents. The BCM signals programmer to activate upper and lower mode valve solenoids, pulling lower mode valve down.

"LOWER" Or ("LWR") Mode

In this mode, air is distributed out lower heater vents and small amount out defroster ducts. The BCM signals programmer to activate lower mode valve solenoids, pulling the lower mode valve up.

"DEFOG" Mode

In this mode, air is distributed equally out defroster and lower heater ducts. The BCM signals programmer to vent lower mode valve, up and down actuators and upper mode valve. This causes lower mode valve to move to a mid-position and upper mode valve to move to a down position.

"DEF" Or ("DEFROST") Mode

In this mode, most air is forced out defroster ducts and small amount out floor ducts. The BCM signals programmer to activate lower mode valve pulling valve down.

"BI-LEV" Or ("BILEV") Mode

In this mode, air is distributed equally out upper (A/C) and lower (floor) ducts. The BCM signals programmer to activate upper mode valve solenoid, allowing vacuum to upper valve actuator.

"R DEFOG" Mode

If equipped with this option, BCM sets time-on requirement and sends signal to programmer. The programmer then sends a signal to rear defogger relay, which turns on heating grid in rear glass. BCM will keep relay energized for 10 minutes. Selecting "R DEFOG" more than once will add 5 minutes each time selected.

TEMPERATURE SENSORS

There are 6 different temperatures monitored by BCM to control climate control system. These temperature values are sent to BCM via thermistors, which decrease in resistance as they get hotter.

In-Car Temperature Sensor

This sensor is located under center A/C outlet. A small amount of in-car air is drawn into sensor housing and over thermistor. Air movement is accomplished by using an aspirator mounted on top of HVAC module.

Airflow from HVAC module creates a slight vacuum at one end of aspirator. This vacuum draws in-car air through temperature sensor housing. Resistance value of sensor is sent to BCM and used in climate control calculations.

Outside Temperature Sensor

This sensor is located at rear of radiator grille, in front of condenser. A temperature memory feature is used in BCM outside temperature sensor programming to help provide greater accuracy under engine restart conditions.

If engine coolant is less than 50°F (10°C) above outside temperature sensor reading, actual sensed outside temperature is displayed. If engine coolant is greater than 50°F (10°C) above sensed reading, memorized outside temperature is displayed. This is the previous temperature sensed when the engine was last running.

At speeds less than 20 MPH, BCM limits displayed temperature value to an increase of one degree every 100 seconds. This compensates for false high temperature readings during heavy traffic or extended idle.

At speeds between 20 to 45 MPH, outside temperature display is allowed to increase but only after a built-in 2 minute sensor cool down time delay. At speeds greater than 45 MPH there is no time delay.

Coolant Temperature Sensor

Coolant temperature sensor is located in intake manifold coolant passage. Its resistance is monitored by ECM, which in turn sends coolant temperature value to BCM over data circuit.

A/C High Side Temperature Sensor

A/C high side temperature sensor is located on high pressure refrigerant line between condenser and orifice tube. By monitoring refrigerant temperature, BCM can determine pressure based upon the pressure-temperature relationship of R-12.

A/C Low Side Temperature Sensor

This sensor is located between orifice tube and evaporator on low pressure refrigerant line. BCM monitors this sensor to determine low side pressure by same method as A/C high side temperature sensor.

Sunload Sensor

Sunload sensor is located under defroster grille, at center base of windshield. This sensor is a thermistor type and senses heat load of sun on vehicle interior. BCM uses this sunload value and compares it to in-car temperature, to determine how much cooling is necessary to maintain selected interior temperature.

LOW REFRIGERANT PRESSURE SWITCH

Low refrigerant pressure switch is located on low pressure refrigerant line. This switch is normally open and closes under pressure. When closed, switch allows ignition circuit to feed compressor clutch relay. If pressure drops below 2-8 psi (.2-.7 kg/cm 2 ), switch opens ignition circuit to relay, shutting system off.

POWER STEERING CUT-OUT SWITCH

Power steering cut-out switch is located on power steering pressure line. It is normally closed and allows ignition circuit to feed compressor clutch relay. If for some reason system pressure exceeds 300 psi (21 kg/cm 2 ), switch will open ignition circuit to relay.

PROGRAMMER

Programmer is located behind glove box, attached to Heat Vent Air Conditioning (HVAC) module. It can be identified by electrical and vacuum connectors attached to it. Contained within programmer are circuits controlling various climate control functions.

These circuits respond to BCM data signals and provide controls for temperature regulation. This is done by a small DC motor, which adjusts air mix door position to blend cold and warm air. Motor provides position feedback signal to BCM, which monitors actual door position.

These circuits also respond to BCM data signals to operate 4 vacuum solenoids mounted within programmer. These solenoids control vacuum to 3 vacuum actuators, which control air inlet door, A/C-defrost door and a 2 position actuator for up-down door.

Programmer circuits also receive blower motor signal from BCM, which transfers it to blower control power module for blower speed operation. These circuits also receive a blower feedback signal used to regulate actual blower speed and voltage.

Programmer also provides a control for rear defogger. When programmer receives a rear defogger signal, it provides a ground to activate rear defogger relay.

AIR MIX VALVE LINKAGE

This linkage consists of a plastic crank arm integral with output shaft of programmer, a serrated nylon retainer and a threaded rod. One end is fastened to air mix door and other end is retained by serrations in nylon retainer to plastic crank arm. Programmer positions air mix door with this rod when BCM sends the appropriate signal.

POWER MODULE

Power module is located on top of evaporator assembly. It provides appropriate power and control to blower motor. Programmer sends a blower signal to power module where it is amplified proportionally to input voltage, then sent to blower motor. Power module is transistorized and provides variable blower speeds. A large heat sink is attached to power module and protrudes into evaporator air stream as a means of cooling.

PROGRAM NUMBER

Program number is a numerical index as to amount of heating or cooling required to meet desired in-car temperature. There are 4 variables, which determine this number: Set temperature of system, outside temperature, in-car temperature and sunload sensor. Program number controls blower speed, air inlet and outlet doors, and is also a factor in determining air mix door position.

This number is calculated by BCM, comparing in-car temperature with set temperature and adjusting result to reflect outside air temperature and sunload.

This program number is calculated frequently to take into account changes in vehicle in-car temperature. When in-car temperature reaches set temperature, system is in equilibrium and BCM strives to keep program number at this point.

Program number is displayed as a number between 0 to 99. A low program number calls for cooling, a high program number calls for heating. Program number can be observed when climate control system is in diagnostic mode. Also, when in this mode, technician can override program number to observe effect on system operation.

AIR MIX DOOR POSITION

The BCM needs to know 3 things before it can calculate air mix door position: Temperature of heated output air, temperature of air conditioned air and temperature delivered air should be. BCM uses coolant temperature to predict the temperature of heated air and average low side temperature to predict the temperature of air conditioned air. If A/C compressor is not working, BCM uses outside air temperature rather than low side temperature signal.

Program number tells BCM how hot or cold delivered air should be. By monitoring a feedback potentiometer on programmer motor, BCM commands programmer to move door until desired position is achieved.

COMPRESSOR CLUTCH CONTROL

Compressor clutch is controlled by ECM through input from BCM. Inputs to ECM are: BCM data, power steering cut-out switch, engine coolant temperature, engine RPM and throttle position sensor.

Inputs to BCM are: ECM data, A/C system setting, outside temperature, in-car temperature, sunload temperature, vehicle speed, low refrigerant pressure switch, A/C high side temperature, and A/C low side temperature.

When all inputs to BCM are within calibrated values, BCM signals ECM on data circuit to allow compressor clutch engagement. ECM then completes path to ground for A/C compressor clutch relay.

A/C compressor clutch control will only engage compressor clutch under these parameters: Climate control is set to "A/C," "AUTO," "BI-LEV" ("BILEV" on CRT models), "DEFOG," or if outside temperature is above 41°F (6°C). Once engaged, compressor clutch engagement time is controlled by BCM as described below.

Extended Compressor At Idle

Smoother idle conditions are obtained by increasing minimum clutch delay time to about 45 seconds whenever vehicle speed drops to less than 15 MPH. This mode is disabled when vehicle speed is greater than 17 MPH.

Normal Compressor On Time

When vehicle operates at a speed greater than 15 MPH, a minimum delay time from 2 to 6 seconds begins before BCM will allow compressor clutch to disengage.

After 2 to 6 seconds, BCM will disengage compressor clutch only if low side temperature is less than 30°F (1°C). After being disengaged, BCM waits for low side to reach a temperature between 45-50°F (7-10°C) and then repeats cycle.

During compressor on time, 7 conditions can cause BCM to disengage A/C compressor clutch: A/C low pressure switch open, A/C high side temperature greater than 199°F (93°C), coolant temperature greater than 259°F (126°C), open or shorted low side temperature sensor, system under or over voltage, wide open throttle signal from ECM, or power steering cut-out switch open.

Under all conditions except wide open throttle signal, compressor will stay disengaged only as long as condition exists. Wide open throttle signal only disengages compressor clutch for a maximum of 20 seconds.

IDLE SPEED CONTROL

To minimize effects of compressor operation on engine idle, ECM modifies engine idle RPM during A/C operation. When ECM receives a compressor engagement signal, it will determine if inputs are within the calibrated area before engaging A/C clutch. If ECM determines inputs are not within specification, it will make an adjustment to idle air control and then engage A/C compressor clutch to compensate for increased engine load.

"LOW REFRIGERANT" MESSAGE

When operating A/C compressor clutch, BCM monitors system inputs for low refrigerant charge. If system charge should fall below one third its capacity, BCM will display "LOW REFRIGERANT" message to warn operator and store a diagnostic trouble code in memory.

"A/C SYSTEM PROBLEM" MESSAGE

If a sensor range, sensor circuit, or BCM calibrated range fails, BCM will display "A/C SYSTEM PROBLEM." In addition to displaying this message, BCM will store a diagnostic code in memory.

COLD PURGE

Cold purge will operate in any mode, except "DEF" ("DEFROST" on CRT models) or "OFF", when coolant temperature is less than 28°F (-2°C). During cold purge, blower motor will be off and any airflow will be directed to front defroster registers to keep breath humidity off windshield. Cold purge will be discontinued when: Program number would result in cooling, or coolant temperature is greater than 110°F (43°C). If either of these conditions exist within 3 minutes of start-up, BCM will automatically resume normal control.

NORMAL PURGE

Normal purge will activate in any mode except "DEF" ("DEFROST" on CRT models) or "OFF." If BCM program number does not result in cooling or intermediate modes and conditions for cold purge do not exist, normal purge will activate.

During normal purge, blower is turned off and any airflow is directed to heater registers with bleed air to A/C registers. To remove all moist air from ducts, blower motor will only run at low speed for several seconds prior to normal operation.

Normal operation will resume when program number would result in cooling or coolant temperature is greater than 110°F (43°C). If within 3 minutes of start-up and neither of these conditions exist, BCM will automatically resume normal operation.

A/C PURGE

A/C purge will activate in any mode except "DEF" or ("DEFROST" on CRT models) or "OFF." If BCM program number results in cooling or intermediate modes and conditions required for either cold purge or normal purge do not exist, A/C purge will activate.

CATHODE RAY TUBE & INSTRUMENT PANEL CLUSTER

Note. If Cathode Ray Tube (CRT) is inoperative, refer to the ENGINE PERFORMANCE section. If the Instrument Panel Cluster (IPC) is inoperative, refer to the appropriate ELECTRONIC INSTRUMENTS article in ACCESSORIES & EQUIPMENT section.

PRELIMINARY PROCEDURES

To properly diagnose climate control system, refer to ECC CLIMATE CONTROL SYSTEM RESPONSE CHART for reference and comparative purposes. (Scheme 3) Diagnosis of all climate control functions must begin with system check. Refer to SYSTEM CHECK CHART at end of this article. (Scheme 10)

Scheme 3

SELF-DIAGNOSTICS

Various inputs to BCM combine with program instructions within system memory to provide accurate control over many subsystems involved. When a subsystem circuit exceeds preprogrammed limits, a system malfunction is indicated and BCM displays an "A/C SYSTEM PROBLEM" message on Driver Information Center (DIC).

To access and control self-diagnostic features, use control panel or CRT. A 20 character display area on DIC is used to display diagnostic information. (Scheme 4)and (Scheme 5). CRT or non-CRT control panel is used to enter diagnostics and access service diagnostic routines.

ENTERING SELF-DIAGNOSTICS

Turn ignition on and depress "OFF" and "WARM" buttons simultaneously for 3 seconds until segment check appears on Driver Information Center (DIC). Select testing desired using panel controls. (Scheme 4)and (Scheme 5). After trouble codes have been displayed, diagnostics can be used to perform several tests on different systems. (Scheme 6)and (Scheme 7).

DATA DISPLAY CODES

Note. Because this article only covers climate control system, only BCM data display codes applying to climate control system are listed.

When trouble shooting, data displays can be used to compare vehicle problems with a vehicle functioning properly. The following is a brief summary of each parameter.

Code BD20, Commanded Blower Voltage

The command blower voltage is read in volts from 0 to system voltage.

Code BD21, Coolant Temperature

The coolant temperature is displayed in degrees Celsius (from -40° to 151°C). These values are obtained from ECM. If there is a failure, failsoft will respond.

Code BD22, Commanded Air Mix Valve Position

The commanded air mix door position is displayed in a percentage. A value close to 0 percent represents a cold air mix door and a value close to 100 percent represents a warm air mix door.

Code BD23, Actual Air Mix Valve Position

The actual air mix door position is displayed in a percentage. This value should follow commanded air mix door position (Code BD22), except when air mix door is commanded beyond its mechanical limits.

Code BD24, Air Delivery Mode

The air delivery mode is displayed as a number from 0 to 13. Each number is a code which represents the following air delivery modes.

AIR DELIVERY MODES

Code BD25, In-Car Temperature Sensor

The in-car temperature is displayed in degrees Celsius (from -40° to 102°C).

Code BD26, Outside Air Temperature

The actual outside temperature is displayed in degrees Celsius (from -40° to 93°C). This value represents actual sensor temperature without any alterations.

Code BD27, High Side Temperature

The high side temperature is displayed in degrees Celsius (from -40° to 215°C).

Code BD28, Low Side Temperature

The low side temperature is displayed in degrees Celsius (from -40° to 93°C).

Code BD32, Sunload Temperature

The sunload temperature sensor is displayed in degrees Celsius (from -40° to 102°C).

Code ED01, Throttle Position Sensor

Throttle position sensor is displayed in percent from 0 to 100.

Code ED04, Coolant Temperature

Coolant temperature is displayed in degrees Celsius (from -40° to 151°C).

INPUT DATA DISPLAY CODE DEFINITIONS

When trouble shooting a malfunction, Instrument Panel Cluster (IPC) input display can be used to determine if switched inputs are properly interpreted. When one of the input tests is selected, the state of that device is displayed as "HI" or "LO". Basically, "HI" or "LO" represent input terminal voltage for that circuit. Also, the display indicates if input changed state since last tested. If a change occurred, an "X" will appear next to "HI" - "LO" indicator. If a change did not occur, an "O" will remain displayed. The "X" will only appear once per selected input.

Code B108, Low Refrigerant Pressure Switch

Low refrigerant pressure switch displays state of switch as "HI" or "LO" voltage inputs to BCM. "HI" indicates refrigerant pressure is present (switch closed) or "LO" indicates low refrigerant pressure (switch open).

Code E178, Power Steering Pressure Switch

Power steering pressure switch ("POWER STRG") display is "LO" when power steering pressure (effort) is high.

OUTPUT DATA DISPLAY CODE DEFINITIONS

When trouble shooting a malfunction, ECM and BCM output cycling can be actuated regardless of inputs and normal program instructions. Once a test is selected, except for ECM Idle Air Control (IAC), test will display "HI" or "LO" for 3 seconds in each state to indicate command and output terminal voltage.

Code E008, A/C Clutch

This function will cycle blower motor to "LO," "ON" and "OFF" every 3 seconds, but only when engine is not running. Coolant fans will cycle regardless of normal control ECM has over high speed. "HI" will be displayed when blower motor is off and "LO" when fan is "ON".

Code BS01, Program Number

When trouble shooting a malfunction, BCM override feature allows testing of certain system functions regardless of normal program instructions. Upon selecting a test, selection's current operation will be represented as a percentage of its full range.

On CRT equipped vehicles, pressing "SLEW" key pad will increase or decrease override value. (Scheme 5)

On non-CRT equipped vehicles, pressing the "COOL" or "WARM" button will decrease or increase override value. (Scheme 4)

On all models, program number can be increased until a value of "99" is reached ("MAX HEAT") or decreased until a value of "0" is reached ("MAX A/C" mode).

Normal program control can be achieved in three ways: Selection of another override test will cancel current override, selection of another system will cancel current override or overriding value beyond values given to particular system.

Override feature or test type is unique in that any other test type within selected system may be active at the same time. After selection of override test, pressing "LEVL" pad on CRT models or fan speed button on non-CRT vehicles, will allow selection of another test type. Control panel will continue to display selected override. When selecting another test type, it is possible to monitor effect of override on different vehicle parameters.

Code ES06, A/C Relay

The A/C relay will be turned "OFF" ("00") or "MAX HEAT" ("99"), by pressing "COOL" or "WARM" button (non-CRT models) or "SLEW" up or down arrow (CRT models).

Code ES07, Blower Motor Relay No. 1

Blower motor relay No. 1 ("FAN REL 1") will be turned "OFF" ("00") or "MAX HEAT" ("99"), by pressing "COOL" or "WARM" button (non-CRT models) or "SLEW" up or down arrow (CRT models).

Code ES08, Blower Motor Relay No. 2

Blower relay No. 2 ("FAN REL 2") will be turned "OFF" ("00") or "MAX HEAT" ("99"), by pressing "COOL" or "WARM" button (non-CRT models) or "SLEW" up or down arrow (CRT models).

Code BS06, Blower Motor Speed

Displays BCM calculated blower motor speed number, expressed as a percent on display. By pressing "COOL" or "WARM" buttons (non-CRT models) or "SLEW" up or down arrows (CRT models), blower speed can be adjusted up or down and blower motor response can be observed. Blower motor of "0" indicates low voltage to blower motor or low speed and "99" full voltage or high speed.

SNAPSHOT DISPLAY

Selecting "SNAPSHOT" test type when in BCM system level will allow recall of up to 3 values recorded at one time for later reference of malfunction codes. (Scheme 6)and (Scheme 7).

Scheme 4

Scheme 5

Scheme 6

Scheme 7

TROUBLE CODE DISPLAY

After "SERVICE MODE" is entered any trouble codes stored in computer memory will be displayed. ECM codes will be displayed first. If no ECM codes are stored, CRT will display "NO ECM CODES" for approximately 2 seconds.

After ECM codes have been displayed BCM codes will be displayed. BCM codes will also be accompanied by "CURRENT" or "HISTORY". "HISTORY" indicates failure was not present when last tested, "CURRENT" indicates fault still exists. This type of information helps in diagnosis of intermittent problems. If no BCM codes are present, BCM will display "NO BCM CODES" message. Trouble codes for ECM, BCM and CRT will be displayed in numerical succession of lowest to highest numbered code.

Note. Operating vehicle in "SERVICE MODE" for extended time periods without engine running can (1) drain battery, (2) possibly relate false diagnostic information and/or (3) cause a no-start condition.

BCM STATUS LIGHTS

While in diagnostic mode, the mode indicators on secondary display are used to indicate status of certain operating modes. Different modes of operation are indicated by status lights being turned "ON" or "OFF". (Scheme 8)

A/C Refrigerant Pressure Status Light

The refrigerant pressure status indicator is turned on when BCM senses low refrigerant pressure switch is open. Status light will remain off if refrigerant pressure and controls are okay. When ambient temperature of low side drops below -5°F (-21°C), status light will come on.

Recirculation Status Light

This indicator light will come on whenever BCM is commanding recirculation mode.

A/C Solenoid Status Light

This indicator light will come on when BCM commands air flow out A/C vents. Light should be on in A/C and bi-level modes.

Air Up Status Light

This indicator light will come on when BCM commands air flow out defroster ducts. Light should be on in defrost and heat/defrost modes.

Air Down Status Light

This indicator light will come on when BCM commands air flow out floor ducts. Light should be on in defrost, heat/defrost and bi-level modes.

A/C Compressor Status Light

This indicator light is turned on when BCM requests ECM to engage A/C compressor clutch.

Scheme 8

Note. Because this article only covers climate control system, ECM codes are not supplied and only BCM codes applying to climate control are listed.

BCM DIAGNOSTIC CODES

CLIMATE CONTROL IN "SERVICE MODE"

When in "Service Mode", climate control will continue to operate in whatever setting it was in prior to "SERVICE MODE". Also, during "SERVICE MODE" operation, system can be operated the same as normal by touching appropriate button(s). (Scheme 4)and (Scheme 5).

After trouble codes have been displayed, "SERVICE MODE" can be used to perform several tests on different systems one at a time. A specific system may be selected for testing, or a segment check can be performed.

System Selection

Following trouble code display, first available system will be displayed, such as ECM. When making system selections there are 3 available alternatives. (Scheme 4)through (Scheme 7).

1. Pressing "OFF" ("LEVL" on CRT models) key pad will stop system selection process and return to beginning of trouble code sequence.
2. Pressing "LO" ("NO" on CRT models) key pad will display next available system selection.
3. Pressing "HI" ("YES" on CRT models) key pad will display system for testing.

Test Type Selection

Having selected a system, the first available test type will be displayed. When making selection of test type, there are 3 available test type alternatives. (Scheme 4)through (Scheme 7).

1. Pressing "OFF" ("LEVL" on CRT models) key pad will stop test type selection and return display to next available system selection.
2. Pressing "LO" ("NO" on CRT models) key pad will display next available test type for selected system. This allows all test type step choices to be considered.
3. Pressing "HI" ("YES" on CRT models) key pad will select displayed test type. Here, display will either indicate selected test type is in progress or first of several specific tests will appear. If "NO DEVICES" appears, test is not available.

Test Selection CRT Models

Selection of "DATA," "INPUTS," "OUTPUTS," or "OVERRIDE" test types will result in first available test being displayed. If dashes ever appear, test is not allowed with engine running. (Scheme 5)and (Scheme 6).

1. Pressing "LEVL" key pad will stop test selection process and return display to next test type for selected system.
2. Pressing "NO" key pad will display next smaller test number. If lowest number is already displayed, highest number will then be displayed.
3. Pressing "YES" key pad will display next larger test number for selected test type. If this key pad is touched and is already at highest number, lowest number will then appear.
4. Pressing "RTN" key pad will exit diagnostics.

Test Selection Non-CRT Models

Selection of "DATA," "INPUTS," "OUTPUTS," or "OVERRIDE" test types will result in first available test being displayed. If dashes ever appear, test is not allowed with engine running. (Scheme 5)and (Scheme 6).

1. Pressing "OFF" button will stop test selection process and return display to next test type for selected system.
2. Pressing "LO" button will display next smaller test number. If lowest number is already displayed, highest number will then be displayed.
3. Pressing "HI" button will display next larger test number for selected test type. If this key pad is touched and is already at highest number, lowest number will then appear.

"CLEAR CODE" Selection

If "CLEAR CODE" test type is selected, it will result in "CODES CLEAR" message being displayed. This message appears for 3 seconds to indicate that all stored trouble codes have been erased from memory. After this 3-second interval, system will automatically return to next available test type for selected system.

Instrument Panel Cluster (IPC) Segment Check

When ignition is on and vehicle is in park, pressing "SYSTEM MONITOR" button on the left switch assembly will cause IPC to sequentially illuminate and blank all segments and telltales on instrument cluster. This may help to determine if all bulbs or segments of IPC are out or always on. To give technician more time to observe segments, when service diagnostics are entered, a total illumination of all segments and bulbs on IPC will occur.

EXITING SELF-DIAGNOSTICS

To get out of "SERVICE MODE" and erase trouble codes, press "RTN" pad on CRT or turn off ignition on CRT models. Press "BI-LEVEL" button or turn off ignition on non-CRT models.

Removal & Installation

1. Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove electrical connections from compressor. Remove front upper pivot bolts.
2. Raise vehicle. Remove splash shield over compressor. Remove 2 compressor adjusting bolts. Remove coupled hose assembly from rear of compressor. Remove compressor. To install, reverse removal procedure. Evacuate and recharge A/C system.

Disconnect negative battery cable. Raise and support vehicle. Remove switch and disconnect wiring. To install, reverse removal procedure.

Note. Switch is mounted on a Schrader valve. It is not necessary to discharge A/C system to replace switch.

Disconnect negative battery cable. Remove cowl shield. Disconnect electrical connection at switch. Remove switch and "O" ring seal. To install, reverse removal procedure.

Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove cowl shield. Disconnect electrical connection at sensor. Remove sensor and "O" ring seal. To install, reverse removal procedure. Evacuate and recharge A/C system.

Outside temperature sensor is located behind center of front grille. Disconnect negative battery cable. Remove radiator upper mounting panel. Remove bolt retaining sensor bracket. Disconnect electrical connection and remove sensor. To install, reverse removal procedure.

1. Disconnect negative battery cable. Remove left side lower dash trim panel and courtesy light. Remove right side lower dash trim panel and courtesy light.
2. Remove steering column lower trim panel. Remove steering column mounting bolts and lower steering column. Remove deflector housings and defroster nozzle grille. Remove screws under defroster nozzle grille.
3. Remove bolts retaining lower instrument panel. Disconnect bulkhead electrical connector. Gently pull instrument panel rearward and remove aspirator hose.
4. Remove fuse panel. Disconnect fuel filler door and trunk release electrical connectors. Disconnect radio antenna lead. Remove instrument panel and place in a protected area. Disconnect sunload sensor electrical connector. Remove sunload sensor.
5. To remove aspirator, remove BCM screws. Disconnect BCM electrical connectors and remove BCM. Remove aspirator duct. Remove aspirator. To install sunload temperature sensor and/or aspirator, reverse removal procedure.

1. Disconnect negative battery cable. Remove cowl shield. Pull engine electrical harness from retainers and position to one side.
2. Remove electrical connector from programmer. Remove screws and remove programmer. To install, reverse removal procedure.

Disconnect negative battery cable. Remove cowl shield. Remove power module electrical connector. Remove screws and remove power module. To install, reverse removal procedure.

Removal

1. Remove cowl shield. Remove bulkhead connector screw and disconnect bulkhead connector. Remove Electronic Spark Control (ESC) connector. Remove ESC mounting screws and remove ESC.
2. Remove power steering support bracket bolts and remove support bracket. Remove ignition coil bracket nuts. Disconnect 3 spark plug wires from coil (cylinders 2, 4 and 6). Disconnect ignition coil primary electrical connectors. Move ignition coil to one side.
3. Remove wiring harness conduits. Remove blower motor cooling tube and electrical connections. Remove blower motor mounting screws. Remove blower motor. To install, reverse removal procedure.

Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove refrigerant lines to evaporator. Remove orifice tube. To install, reverse removal procedure. Evacuate and recharge A/C system.

1. Disconnect negative battery cable. Drain radiator coolant. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove top engine mount brackets to gain access to cooling fan. Remove cooling fan mount bolts. Disconnect electrical connections and remove cooling fan.
2. Remove radiator hoses. Remove transaxle oil cooler pipes. Remove radiator panel mounting bolts. Disconnect coolant recovery hose and remove radiator.
3. Disconnect condenser refrigerant lines. Remove refrigerant line retaining bracket. Remove condenser mount bolts. Remove condenser. To install, reverse removal procedure. Fill cooling system. Evacuate and recharge A/C system. Check for leaks.

Perform steps 1) and 2) of CONDENSER removal and installation procedures. Remove hose assembly retaining bolt at rear of A/C compressor. Disconnect hose at condenser and accumulator. Remove hose assembly. To install, reverse removal procedure. Fill cooling system. Evacuate and recharge A/C system.

Disconnect negative battery cable. Discharge A/C system using approved refrigerant recovery/recycling equipment. Remove accumulator guard. Remove refrigerant lines at accumulator. Remove accumulator assembly. To install, reverse removal procedure. Evacuate and recharge A/C system.

1. Remove blower motor. See BLOWER MOTOR removal and installation procedure. Remove A/C line assembly bracket bolt, bracket and line assembly from evaporator.
2. Remove power module electrical connector, retaining screws and power module. Disconnect heater hoses from heater core and move heater hoses to one side.
3. Raise and support vehicle. Remove heat shield screws. Bend heat shield to allow for removal of power module plastic cover. Lower car. Remove plastic cover screws and remove plastic cover. Remove housing retaining screws.
4. Working inside car, remove right side sound insulator screws. Remove right side courtesy light and remove sound insulator. Remove floor air outlet screws and remove air outlet.
5. Pull carpet back on right side. Working behind carpet, remove nuts and bolts retaining A/C housing.
6. Working in engine compartment, remove A/C housing. Remove evaporator retaining screw. Remove evaporator. To install, reverse removal procedure. Fill cooling system. Evacuate and recharge A/C system.

1. Perform steps 1) through 4) of SUNLOAD TEMPERATURE SENSOR & ASPIRATOR removal and installation procedures. Drain radiator coolant. Disconnect heater hoses at heater core and move to one side.
2. Remove programmer retaining screws, electrical connections and vacuum hoses. Remove programmer. Remove power module retaining screws. Disconnect power module electrical connections and remove power module.
3. Remove heater core cover screws and remove cover. Remove heater core retaining clips. Remove heater core retaining screws. Remove heater core. To install, reverse removal procedure. Fill cooling system.

Disconnect negative battery cable. Remove right and left sound insulators. Remove right and left courtesy lights. Remove Orange vacuum hose from valve actuator. Remove valve actuator retaining nuts and remove valve actuator. To install, reverse removal procedure.

Remove right and left sound insulators. Remove Yellow vacuum hose from valve actuator. Remove valve actuator. To install, reverse removal procedure.

1. Perform steps 1) through 4) of SUNLOAD TEMPERATURE SENSOR & ASPIRATOR removal and installation procedures. Remove 3 instrument panel wiring harness conduit nuts and remove conduit.
2. Remove floor air outlet screws and remove floor air outlet. Remove defroster nozzle distribution assembly vacuum hoses. Remove defroster nozzle distribution nozzle retaining screws. Remove defroster air distribution assembly.
3. Disconnect vacuum hoses from valve actuator. Remove valve actuator retaining bolts and remove valve actuator. To install, reverse removal procedure.

SYSTEM CHECK CHART

Review text starting with title USING SELF-DIAGNOSTICS through to EXITING SELF-DIAGNOSTICS before proceeding with SYSTEM CHECK CHART.

Scheme 9

CHART 1 - COMPRESSOR WON'T ENGAGE

A/C compressor clutch is supplied battery voltage through a fusible link. This voltage is supplied through a 20 amp A/C fuse, through a relay grounded by ECM. Power steering pressure switch and low refrigerant pressure switch must be closed.

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks if low side temperature sensor is responding properly.
2. This step checks if fault is in control to relay, or control to A/C clutch.
3. This step checks if fault is in feed wire to relay.
4. This step checks if fault is in control of relay, or relay.
5. This step checks if fault is due to an open or short in circuit No. 762, or short in circuit or ECM.
6. This step checks if fault is due to open in circuit No. 50 to relay, or electrical feed to A/C clutch.
7. This step checks if fault is due to A/C clutch or A/C power and ground circuits.

Scheme 10

CHART 2 - COMPRESSOR ALWAYS ENGAGED

A/C compressor clutch is supplied battery voltage through a fusible link. This voltage is switched by a 20 amp A/C fuse, through a relay grounded by ECM. Power steering pressure switch and low refrigerant pressure switch must be closed.

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks if fault is due to mechanical binding of A/C clutch, grounded control signal, or faulty ECM.
2. This step checks if fault is due to mechanical binding of A/C clutch, or faulty circuits.

Scheme 11

CHART 3 - HIGH SPEED BLOWER SPEED ONLY

Based on a signal from BCM, programmer sends a variable voltage signal to power module. Power module then amplifies signal and sends signal to blower motor. Programmer monitors blower voltage and adjusts signal to achieve proper blower speed.

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks if fault is due to faulty feedback signal, or faulty blower signal.
2. This step checks if fault is due to programmer, including terminal contacts or open in signal circuit, including BCM.

Scheme 12

CHART 4 - NO BLOWER OPERATION

Based on a signal from BCM, programmer sends a variable voltage signal to power module. Power module then amplifies signal and sends signal to blower motor. Programmer monitors blower voltage and adjusts signal to achieve proper blower speed.

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks if fault is due to blower signal circuit to programmer, or circuits used by blower control.
2. This step checks if fault in control is due to short in circuit No. 754, including programmer and circuits.
3. This step checks if fault in control is due to open in circuit No. 754, or rest of control circuits.
4. This step checks if fault is due to open in blower motor ground, including blower motor and control circuits.
5. This step checks if fault in blower control is due to open in power module feed or short in blower motor feed, including terminal contact and excessive blower motor current draw.
6. This step checks if fault in blower motor is due to short in circuit No. 760, programmer or BCM.

Scheme 13

CHART 5 - AIRFLOW FROM WRONG DUCT

BCM will direct blended air in one of several air delivery modes. While side window outlets receive air during all modes, other outlets are directed air by commanding programmer to energize specific vacuum valves feeding appropriate combination of mode valve actuators. BCM determines proper air delivery mode based on current program number and control panel setting.

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks commanded door position so actual air delivery can be checked.
2. This step checks if fault is due to vacuum source or distribution of vacuum.
3. This step checks if fault is due to vacuum circuit leaks, stuck doors or faulty programmer.

Scheme 14

CHART 6 - INSUFFICIENT HEAT AT MAXIMUM HEATING

Note. Step numbers are for air mix valve adjustment.

1. Remove glove box to gain access to programmer.
2. Lift straight up on air mix valve link to release it from programmer arm.
3. Turn on ignition and select 90°F. Wait for programmer arm to stop moving.
4. Manually pull air mix valve link toward passenger door until it hits mechanical stop.
5. With both air mix valve link and programmer arm in maximum heat position, snap air mix valve link back into programmer arm.
6. Visually check movement by selecting different temperature settings.

Scheme 15

CHART 7 - INSUFFICIENT COOLING AT MAXIMUM COOL

Note. Step numbers are for air mix valve adjustment.

1. Remove glove box to gain access to programmer.
2. Lift straight up on air mix valve link to release it from programmer arm.
3. Turn on ignition and select 65°F ( DO NOT select 60°F). Wait for programmer arm to stop moving.
4. Manually pull air mix valve link toward passenger door until it hits mechanical stop.
5. With both air mix valve link and programmer arm in maximum heat position, snap air mix valve link back into programmer arm.
6. Visually check movement by selecting different temperature settings.

Scheme 16

CHART 8 - IMPROPER TEMPERATURE REGULATION

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks if improper temperature regulation is due to air mix valve movement.
2. This step checks if improper temperature regulation is due to poor aspirator airflow. Procedure for checking aspirator airflow is as follows: Engine running with vehicle NOT in direct sunlight. Select high blower speed and any mode EXCEPT "DEF". Hold paper strip by one end with opposite end over in-car temperature sensor air inlet. Raise paper strip until it is about 1/2" below inlet. If aspirator airflow is good, paper will be sucked down over inlet.
3. This step checks accuracy of in-car temperature sensor.
4. This step checks air mix valve adjustment. Remove glove box to gain access to programmer. Lift straight up on air mix valve link to release it from programmer arm. Turn on ignition and select 90°F. Wait for programmer arm to stop moving. Manually pull air mix valve link toward passenger door until it hits mechanical stop. With both air mix valve link and programmer arm in maximum heat position, snap air mix valve link back into programmer arm. Visually check movement by selecting different temperature settings.
5. This step checks if binding is due to valve or motor.

Scheme 17

Scheme 18

CHART 10 - REAR DEFOGGER INOPERATIVE

The rear defogger is activated by "R DEFOG" button on control panel. When pressed, a signal is sent to BCM on circuit No. 800. BCM calculates "ON" time for rear defogger and sends a serial signal to programmer. Programmer then supplies ground to activate relay "D".

Note. Test numbers refer to test numbers on diagnostic charts.

1. This step checks if BCM is able to send and receive serial data between programmer and ECC control panel.
2. Since signal from "R DEFOG" button is serial, this step checks to see if button is functional by using it to exit diagnostics.
3. This step checks for power at both relay terminals.
4. This step checks for an open in circuit No. 291, or faulty programmer. Test light should glow when "R DEFOG" button is pressed. This verifies serial signal was processed and ground was supplied by programmer to relay "ON" circuit No. 291.
5. This step checks if fault is in relay, output to defogger or ground. Normally by jumping terminals, defogger will operate.

Scheme 19

CODE B110 - OUTSIDE TEMPERATURE SENSOR FAILURE

Outside air temperature sensor is a thermistor located behind grille. Sensor senses outside air temperature for BCM. The BCM applies a voltage on circuit No. 735 to the sensor. When sensor is cold, its resistance is high. BCM will see a high signal voltage. As sensor warms, its resistance becomes less and signal voltage is pulled low through sensor ground (circuit No. 736). This signal voltage will vary between 5 volts (open circuit) and 0 volts (shorted circuit).

Code B110 will set if ignition switch is "ON" and signal voltage is less than "-38°C" (open circuit) or more than "55°C" (shorted circuit). During time failure is present, a substitute temperature reading will be implemented to allow continued operation of climate control system (continuous compressor at idle will be disabled). Outside air temperature display Code BD26 will display actual sensor reading in degrees Celsius. See DATA DISPLAY CODES under TESTING.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Check to see if open circuit reading is due to circuit or sensor. If open circuit reading changes to short circuit reading after jumping sensor terminals, BCM and wiring are okay.
2. By applying a ground to various points in circuits, an open can be isolated by observing if parameter display changes from open reading to shorted reading.
3. Check to see if short circuit reading is due to circuit or sensor. If short circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.

Notes On Intermittents

If ambient temperature drops less than approximately "-38°C," Code B110 should be ignored. If Code B110 is set with any of the following Codes, B119, B120, B122, B132, or B440, the most likely cause is an intermittent open in circuit No. 736.

If an intermittent Code B110 is set, check Code B110 data display value for outside temperature (Code BD26). If Code BD26 value is less than "-38°C," code was caused by an open in circuit No. 735, 736, or outside temperature sensor. If Code BD26 value is greater than "55°C," code was caused by a short to ground on circuit No. 735 or shorted outside air temperature sensor. Wiggle related wiring while observing data display Code BD26. If failure is induced, reading will jump from its normal value to a reading outside range of "-38°C" to "55°C."

If Code BD26 display is not reasonably close to actual temperature of air at sensor, check for poor terminal contact or replace sensor.

Scheme 20

CODE B111 - A/C HIGH SIDE TEMPERATURE SENSOR FAILURE

A/C high side temperature sensor is a thermistor that senses refrigerant system high side (condenser outlet) temperature from BCM. BCM applies a voltage on circuit No. 732 to the sensor. When sensor is cold, its resistance is high. BCM will see a high signal voltage. As sensor warms, its resistance becomes less and signal voltage is pulled low through sensor ground (circuit No. 736). This signal voltage will vary between 5 volts (open circuit) and 0 volts (shorted circuit).

Code B111 will set if ignition is on, outside air temperature sensor has not failed and reads more than 32°F (0°C), and signal voltage indicates less than "-30°C" (open circuit) or more than "184°C" (shorted circuit). During time failure is present a substitute temperature reading will be implemented to allow continued operation of climate control system and engine cooling fans will be forced to high speed if A/C clutch is on. A/C high side temperature reading (data display Code BD27) will display actual sensor reading in degrees Celsius.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Check to see if open circuit reading is due to circuit or sensor. If open circuit reading changes to a short circuit reading after jumping sensor terminals, BCM and wiring are okay.
2. By applying a ground to various points in circuits, open can be isolated by observing when parameter display changes from open reading to shorted reading.
3. Check to see if short circuit reading is due to circuit or sensor. If short circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.

If an intermittent Code B111 is being set, check Code B111 data display value for high side temperature (data display Code BD27). See DATA DISPLAY CODES under TESTING. If Code BD27 value is less than "-30°C," code was caused by an open in circuit No. 736, or high side temperature sensor. If Code BD27 value is greater than "184°C," code was caused by a short to ground on circuit No. 732 or a shorted high side temperature sensor. Wiggle related wiring while observing data display Code BD27. If failure is induced, reading will jump from its normal value to reading outside a range of "-30°C" to "184°C."

If Code BD27 value displayed is not reasonably close to corresponding gauge pressure reading, check for poor terminal contact or replace sensor.

Scheme 21

CODE B112 - A/C LOW SIDE TEMPERATURE SENSOR FAILURE

A/C low side temperature sensor is a thermistor that senses refrigerant system low side (evaporator inlet) temperature for BCM. BCM applies a voltage on circuit No. 731 to sensor. When sensor is cold resistance is high. BCM will see a high signal voltage. As sensor warms, its resistance becomes less and signal voltage is pulled low through sensor ground (circuit No. 736). This signal voltage will vary between 5 volts (open circuit) to 0 volts (shorted circuit).

Code B112 will set if ignition on, outside temperature sensor has not failed and reads more than 32°F (0°C), and signal voltage indicates less than "-38°C" (open circuit) or more than "94°C" (shorted circuit). During time failure is present a substitute temperature reading (same value as outside air temperature) will be implemented to allow continued operation of climate control system. Computer clutch will be disabled. A/C low side temperature reading (data display Code BD28), will display actual sensor reading in degrees Celsius. See DATA DISPLAY CODES under TESTING.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Check to see if open circuit reading is due to circuit or sensor. If open circuit reading changes to a short circuit reading after jumping sensor terminals, BCM and wiring are okay.
2. By applying a ground to various points in circuits, an open can be isolated by observing whether parameter display can be changed from open reading to shorted reading.
3. Check to see if short circuit reading is due to circuit or sensor. If short circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.

If an intermittent Code B112 is set, check Code B112 data display value for low side temperature (data display Code BD28). If Code BD28 value is less than "-38°C," code was caused by an open circuit in circuit No. 731, 736, or low side temperature sensor. If Code BD28 value is more than "94°C," code was caused by a short to ground on circuit No. 731 or a shorted low side temperature sensor. Wiggle related wiring while observing Code BCM data display Code BD28. If failure is induced, reading will jump from its normal value to a reading outside range of "-38°C" to "94°C."

If value of sensor displayed by Code BD28 is not reasonably close to corresponding gauge pressure reading, check for poor terminal contact or replace sensor.

Scheme 22

CODE B113 - IN-CAR TEMPERATURE SENSOR FAILURE

In-car temperature sensor is a thermistor that senses interior temperature for BCM. BCM applies a voltage on circuit No. 734 to sensor. When sensor is cold its resistance is high. BCM will see a high signal voltage. As sensor warms, its resistance becomes less and signal voltage is pulled low through sensor ground (circuit No. 736). This signal voltage will vary between 5 volts (open circuit) to 0 volts (shorted circuit).

Code B113 will set if ignition is on, outside temperature sensor has not failed, outside temperature is more than 32°F (0°C) and signal voltage indicates less than "-36°C" (open circuit), or more than "97°C" (shorted circuit). During time failure is present a substitute temperature reading will be implemented to allow continued operation of climate control system. In-car temperature reading data display Code BD25, will display actual sensor reading in degrees Celsius.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Check to see if open circuit reading is due to sensor or circuit. If open circuit reading changes to a short circuit reading after jumping sensor terminals, BCM and wiring are okay.
2. By applying a ground to various points in circuits, an open can be isolated by observing whether parameter display can be changed from open reading to short reading.
3. Check to see if short circuit reading is due to circuit or sensor. If shorted circuit reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.

If an intermittent Code B113 is being set, check Code B113 data display value for in-car temperature (Code BD25). If data display Code BD25 value is less than "-36°C," code was caused by an open in circuit 734, 736, or in-car temperature sensor.

If Code BD25 value is over "97°C," code was caused by a short to ground on circuit No. 734 or a shorted in-car temperature sensor. Wiggle related wiring while observing data display Code BD25. If failure is induced, reading will jump from its normal value to a reading outside range of "-36°C" to "97°C".

If value displayed by Code BD25 is not reasonably close to actual temperature of air at sensor, check for proper terminal contact or replace sensor.

Scheme 23

CODE B115 - SUNLOAD TEMPERATURE SENSOR TEST

Sunload sensor is a thermistor that senses intensity of sunlight hitting car. BCM applies a voltage on circuit No. 590 to sensor. When sensor is cold its resistance is high. BCM will see a high signal voltage. As sensor warms, its resistance becomes less and signal voltage is pulled low through sensor ground (circuit No. 736). This signal voltage will vary between 5 volts (open circuit) to 0 volts (short circuit).

Code B115 will set if ignition is on, outside temperature sensor has not failed, outside temperature is more than 32°F (0°C) and signal voltage indicates less than "-35°C" (open circuit) or more than "94°C" (shorted circuit). During time failure is present, BCM will disregard sunload sensor temperature reading for climate control operation. Sunload temperature reading data display Code BD32, will display actual sensor reading.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Check to see if open circuit reading is due to circuit or sensor. If open circuit reading changes to a short circuit reading after jumping sensor terminals, BCM and wiring are okay.
2. By applying a ground to various points in circuits, an open can be isolated by observing when parameter display changes from open reading to short reading.
3. Check to see if short circuit reading is due to circuit or sensor. If shorted sensor reading changes to an open circuit reading after disconnecting sensor, BCM and wiring are okay.

If an intermittent Code B115 is being set, check Code B115 data display value for sunload temperature (Code BD32). If Code BD32 value is less than "-32°C," code was caused by an open in circuit No. 590, 736, or sunload temperature sensor. If Code BD32 value is more than "94°C," code was caused by a short to ground on circuit No. 590 or a shorted sunload temperature sensor. Wiggle related wiring while observing data display Code BD32. If failure is induced, reading will jump from its normal value to a reading outside range of "-35°C" to "94°C".

If temperature of sensor, displayed by Code BD32 is not reasonably close to a corresponding thermometer reading, check for poor terminal contact or replace sensor.

Scheme 24

CODE B440 - AIR MIX DOOR CIRCUIT PROBLEM

Code B440 is set by BCM if it is unable to move the air mix door to within 2 percent of the commanded position in 60 seconds. BCM requests door to move over data circuit No. 800. With ignition "ON," BCM supplies 5 volts on circuit No. 705 and ground on circuit No. 736. BCM monitors a feedback pot on air mix motor which varies from 0 to 5 volts, depending on door position. If door is requested to move but feedback voltage does NOT change after 2 minutes, BCM stores Code B440. The code will not set if there is a current Code B337.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Data display Code BD23 displays actual air mix door position. Normal range is between 1 percent and 99 percent. BCM override value Code BS01 is for program number. As program number is changed from 0 (maximum cooling) to 99 (maximum heating), door position should vary between its limits of travel.
2. This step checks if fault is due to the 5 volt reference and ground circuit, or the feedback signal circuit.
3. This step checks if fault is due to programmer or sensor circuit.
4. This step checks if faults are due to circuit or BCM.
5. This step checks if open circuit reading is due to circuit No. 736 or 705.

If an intermittent Code B440 is being set, check Code B440 data display Code BD23. If it was 0 percent, check for an intermittent open in circuit No. 736. If it was 100 percent, check for an intermittent circuit No. 733 or 705.

If it was 1 to 99 percent, check for binding door movement throughout range of door travel and check for a poor ground in circuit No. 803. Wiggle related wiring while observing actual air mix door position (data display Code BD23) movement. If failure is induced, valve (door) position will either stop or jump to an extreme value (0 or 100 percent). This will help in isolating location of malfunction.

Scheme 25

CODES B446/B447/B448 - REFRIGERANT SYSTEM PROBLEM

BCM monitors certain system inputs for an indication of low refrigerant charge. If system refrigerant state of charge should fall below approximately one third its capacity, BCM is capable of detecting this condition and will display a "LOW A/C REFRIGERANT" or "VERY LOW A/C REFRIGERANT - A/C COMP DISENGAGED" message to warn driver.

BCM determines state of charge by its low side temperature sensor and low refrigerant pressure switch. Since temperature and pressure are proportionally related in A/C system, low temperature is same as low pressure. In addition to message, BCM will store in memory a Code B446, B447, or B448 to indicate a low refrigerant condition was detected.

Code B446 will set if low side temperature drops too quickly during compressor engagement. Code B447 will set if low side temperature drops too quickly during compressor engagement or low refrigerant pressure switch opens during compressor engagement. Code B448 will set if low refrigerant pressure switch remains open for more than 3 minutes.

Note. Test numbers refer to test numbers on diagnostic charts.

1. Input data display Code BD108 displays voltage state of circuit at BCM.
2. This checks to see if open circuit reading is due to circuit or switch.
3. This checks to see if fault is on ignition side or BCM side of switch circuit.
4. This checks to see if fault is due to pressure switch or low refrigerant charge.

Scheme 26

CODES B446/B447/B448 - REFRIGERANT SYSTEM PROBLEM (CONT.)

If problem has been determined not to be in low refrigerant switch circuit proceed with the following test.

Note. Test numbers refer to test numbers on diagnostic charts.

1. This is a test to determine if A/C low refrigerant pressure switch opens when compressor is running. If data display Code BD108 remains "HI" during compressor engagement, then system fault is due to refrigerant.
2. This checks if switch is opening due to low refrigerant pressure charge or switch.

If Code B446 and/or B448 are both set, check low side temperature sensor and circuitry. If okay, evacuate and recharge system. If Code B447 and/or B448 are both set, check low refrigerant pressure switch and circuitry.

Scheme 27

CODE 449 A/C HIGH TEMPERATURE CHECK

Code B449 is designed to disengage A/C compressor clutch in the event high side refrigerant temperature exceeds 199°F (93°C). A/C compressor clutch will come back when high side temperature falls below 199°F (93°C). Causes for excessive high A/C head pressure should be checked.

Scheme 28

Climate Control A/C-Heater Wiring Diagram. Scheme 29