DESCRIPTION
The Digital Fuel Injection (DFI) system combines engine control, fuel metering and emission monitoring into a computer-controlled system. The Electronic Control Module (ECM) is the brain of the DFI system. The ECM is a digital electronic computer which receives and processes engine data, computes and interprets engine information, and sends instructions to various components. It provides fuel efficient operation with reduced exhaust emissions.
The Eldorado and Seville are also equipped with a Body Control Module (BCM) that is used to control various vehicle functions based upon data sensors and switch inputs. The ECM and BCM exchange information to maintain efficient operation of all vehicle functions. This transfer of information gives the BCM control over the ECM's self-diagnostic capabilities as well as its own.
| CAUTION | Power should never be removed or applied to ECM or BCM with ignition switch turned to "ON" position. Before removing or connecting battery cables, fuses, or ECM/BCM connectors, always turn ignition switch to "OFF" position to prevent damage to modules. |
The DFI system consists of the following sub-systems: fuel delivery, air induction, data sensors, Electronic Control Module (ECM), Body Control Module (BCM), Electronic Spark Timing (EST), Idle Speed Control (ISC), emission controls, closed loop fuel control, cruise control, diagnostic system, catalytic converter, and Viscous Converter Clutch (VCC).
FUEL DELIVERY
Fuel delivery system consists of an electric in-tank fuel pump (integral part of fuel sending unit), fuel filter, fuel pressure regulator, fuel injectors and fuel lines. Fuel is supplied to engine through 2 electronically pulsed (timed) injector valves located in throttle body on top of intake manifold. The ECM controls the amount of fuel metered through injectors based upon engine demand information.
AIR INDUCTION
The air induction system consists of a throttle body and intake manifold. Air for combustion enters throttle body and is distributed to each cylinder through intake manifold. Throttle body contains a skirt below each injector to improve fuel distribution. Airflow is controlled by throttle valves, which are connected to accelerator linkage. Idle speed is determined by position of throttle valves and is controlled by the Idle Speed Control (ISC) motor.
INPUT DATA SENSORS
Each sensor furnishes electronic impulses to ECM. (Scheme 1) The ECM computes spark timing and fuel delivery rate necessary to maintain desired air/fuel ratio. Sensor operation is as follows
DFI/ECM System Control Schematic. Scheme 1
Manifold Air Temperature (MAT) Sensor
The MAT sensor is located in the intake manifold directly in front of the throttle body unit. Sensor measures air/fuel mixture temperature in intake manifold. Sensor is a thermistor whose resistance changes as air temperature changes. Low temperature produces high resistance. The ECM interprets the varying resistance as changes in air/fuel mixture temperatures. This information is used by the ECM for computing injector pulse width adjustments.
Coolant Temperature Sensor (CTS)
The CTS provides information to ECM which is used for fuel enrichment, ignition timing, EGR operation, canister purge control, air management, early fuel evaporation control, idle speed control and closed loop fuel control. Like the MAT sensor, it is a thermistor type variable resistor. Its resistance decreases as temperature rises.
Manifold Absolute Pressure (MAP) Sensor
The MAP sensor is mounted on a bracket located directly behind throttle body assembly. A hose from throttle body to MAP sensor provides vacuum signal. Sensor monitors changes in intake manifold pressure (vacuum) which result from engine load and speed variations.
As intake manifold pressure increases (vacuum drops), additional fuel is required by engine. The MAP sensor sends this information to ECM, and ECM increases injector pulse width (injector "on" time). As pressure decreases, pulse width is decreased. The ECM uses this information to control fuel delivery and ignition timing.
Throttle Position Sensor (TPS)
The Throttle Position Sensor (TPS) is connected directly to throttle shaft. TPS is a variable resistor mounted on side of throttle body. Sensor receives a reference voltage from the ECM and based on throttle position, will allow part or all of this reference signal voltage to ground at the ECM. At closed throttle, sensor resistance is high. The ECM will see a returned voltage of only about .5 volt. As throttle angle increases, resistance decreases and the ECM sees an increasing voltage signal, of up to 5 volts, at wide open throttle. The ECM uses this signal to determine injector pulse width.
Throttle Switch
The throttle switch is an integral part of the Idle Speed Control (ISC), it indicates to the ECM that the throttle position is at idle. The ECM will then control idle speed via the ECM.
Vehicle Speed Sensor (VSS)
Sensor is a permanent magnet pulse generator that informs ECM of vehicle speed. Speed sensor produces a weak voltage signal (4000 pulses per mile) which is amplified by a buffer amplifier. The speed sensor is mounted in the transmission, and the buffer amplifier is under right side of dash. The ECM uses vehicle speed sensor signals for logic required to operate fuel economy data panel, integral cruise control, and idle speed control.
Oxygen (O2) Sensor
The oxygen sensor used in DFI is a closed-end Zirconia sensor placed in the exhaust gas stream. This sensor produces a very weak voltage which varies with oxygen content of exhaust gases. As oxygen content of exhaust gases increases, a leaner mixture is indicated by low voltage output. As oxygen content decreases, a richer mixture is indicated by higher voltage output. Typical voltage variation should be between about 100 and 900 millivolts. The ECM corrects air/fuel ratio in response to changes in these voltage signals.
Note. If oxygen sensor output voltage is measured, a high impedance digital voltmeter with a minimum input impedance of 5 megohms MUST be used. Use of a meter with lower impedance rating can cause inaccurate readings or damage to the sensor unit.
Engine Speed Sensor (Distributor Reference Signal)
The engine speed sensor signal comes from a 7-terminal High Energy Ignition (HEI) module in the distributor. Pulses from distributor are sent to ECM where time between pulses is used to calculate engine speed. The ECM adds spark advance modifications to signal, and sends this signal back to distributor.
Power Steering Pressure Switch (PSPS)
The ECM monitors power steering pressure in order to raise idle speed during power steering use. The power steering switch is normally closed and sends a 12 volt signal to the ECM. When steering pressure increases, the switch opens and breaks the signal to the ECM.
Park/Neutral Safety Switch
The park/neutral safety switch sends a signal to the ECM that the vehicle transmission is in Park or Neutral. This signal is used to select idle speed signals. This switch is a part of the Neutral Safety Back-Up (NSBU) switch.
Crank Signal
Starter solenoid sends a signal to the ECM during starting and cranking operation. This signal is used to enable starting mode signals. If this signal is not present, vehicle may be hard to start.
Transmission Temperature & 3rd-4th Gear Switch
These switches supply signals to the ECM to be used for Viscous Converter Clutch (VCC) control. A high transmission fluid temperature of 315°F (157°C) will cancel VCC operation.
Cruise Control
The ECM receives input signals from cruise control engagement switches, instrument panel switch, brake release switch, drive switch and speed sensor. These signals are used by the ECM to control cruise control operation.
ELECTRONIC CONTROL MODULE (ECM)
The ECM is located under instrument panel, on passenger's side. The ECM controls all DFI system functions. It constantly monitors sensors and controls the systems that affect vehicle performance. The ECM contains a Memory-Calibration (MEM-CAL) unit.
The MEM-CAL unit has calibration information based on vehicle's weight, engine, axle ratio, and several other factors. Always check manufacturer's latest service parts information to ensure the correct MEM-CAL unit is installed when replacing or servicing ECM.
Poor engine performance, idle or part throttle surges, loss of cruise control, flashing "ENGINE CONTROL SYSTEM" telltale, or hard/no starts may be encountered if MEM-CAL unit is poorly installed. If the MEM-CAL unit is missing or incorrectly installed, a code "B344" will be displayed by the BCM.
Electronic Spark Timing (EST)
The EST system consists of ECM and High Energy Ignition (HEI) distributor with HEI module. The HEI distributor communicates to ECM through a 4-terminal connector which contains 4 circuits: distributor reference circuit, by-pass circuit, EST circuit, and ground circuit.
Whenever pick-up coil signals HEI module to open primary circuit, it also sends spark timing signals to ECM through the reference line. When voltage on HEI by-pass line is zero volts (engine cranking), HEI module switches to by-pass circuit. In by-pass circuit, HEI module provides spark advance at base timing and disregards spark advance signal from ECM. When voltage on HEI by-pass circuit is 5 volts (engine running at about 400 RPM), HEI module accepts spark timing signal provided by ECM.
The ECM monitors engine speed through the HEI reference line and engine operating conditions through data sensors. From these parameters, ECM calculates proper spark advance and supplies signals to HEI distributor through the EST line.
Idle Speed Control (ISC)
The ISC motor is an electrically driven actuator which changes throttle valve angle (in idle position) according to commands from ECM. This function is by-passed when throttle is opened enough to bring TPS off its idle circuit. When engine is cold, ECM holds throttle valve open for longer period of time to provide faster warm-up. The ISC motor is located at front or on side of throttle body.
Emission Controls
The ECM controls operation of EGR system, AIR management system and canister purge control operation. (Scheme 1) Description of each system is as follows
- EGR System Signals received from coolant sensor provide ECM with engine temperature data. When engine is cold, ported vacuum to EGR is closed with a solenoid valve. When engine is warm, solenoid valve is opened and EGR is allowed.
- AIR Management System Control of this system is similar to that of the EGR system. When engine is cold, ECM energizes an air control solenoid which allows air to flow to air switching valve. Switching valve is energized by ECM to direct air to exhaust ports to aid in quickly heating oxygen sensor to 600°F (316°C). When engine is warm or in closed loop operation, ECM de-energizes air switching valve and air is sent directly to catalytic converter to assist in oxidation of HC and CO. If the air control valve detects a rapid increase in manifold vacuum (deceleration), if certain operating modes exist or if ECM detects any failure in the system, air is diverted to air cleaner or dumped to atmosphere.
- Canister Purge Control Operation Vacuum to canister purge control valve is controlled by ECM with a solenoid valve. When engine is in open loop operation, solenoid valve is energized and vacuum is blocked to purge valve. When system is in closed loop operation, solenoid valve is de-energized and vacuum can be applied to purge valve to draw collected vapors into intake manifold.
Viscous Converter Clutch (VCC) System
A solenoid operated valve in the transmission is used to hydraulically couple the torque converter to the transmission input shaft. This allows less slippage loss and greater fuel economy. The solenoid is controlled by the ECM and is influenced by vehicle speed, transmission fluid temperature, coolant temperature, throttle position, 3rd-4th gear switch, and barometric pressure.
Cruise Control Solenoids
The ECM processes cruise control inputs together with DFI engine control inputs and transmits command signals to vacuum control solenoid valve and power unit solenoid valve to control vehicle speed.
A/C Relay
The ECM controls the A/C compressor relay. Input signals from engine load and temperature sensors are used to influence control of the relay by the ECM.
Fuel Pump Relay
The ECM will turn the fuel pump relay on for 2 seconds when the ignition switch is turned to the "RUN" position. If the engine is not cranked within 2 seconds the ECM will shut the fuel pump off. The fuel pump will be reactivated when the key is turned to the "START" position.
Fuel Injectors
The fuel injector solenoids are controlled by the ECM. The solenoid operates a check valve, which controls fuel supply to the injector nozzle. A constant fuel pressure is supplied to the injector and fuel supply is controlled by the amount of time the solenoid is activated.
BCM Module
At the heart of the BCM/ECM computer system, is the Body Computer Module (BCM). The BCM is located in the middle of the instrument panel, behind the Climate Control/Driver Information Center (CCDIC). (Scheme 2)
The BCM has an internal microprocessor which links the BCM with all other components in the system. All system sensors and switches are monitored by the BCM or one of 4 major components that complete the BCM/ECM computer system.
In order to control and access the self-diagnostic features available to the BCM, 4 additional electronic components are utilized: the Engine Control Module (ECM), the Instrument Panel Cluster (IPC), the Heating Ventilation and A/C (HAVC) programmer, and the (CCDIC).
A combination of inputs from these 4 major components and other sensors and switches communicate with the BCM. The data communication gives the BCM control over the ECM's self-diagnostic capabilities in addition to its own.
Climate Control/Driver Information Center (CCDIC). Scheme 2
"ENG CONTROL SYSTEM/SERV SOON/SERVICE NOW" TELLTALES
The "ENGINE CONTROL SYSTEM" telltale light indicates a problem or system malfunction. Depending on the trouble code set, either the "SERVICE SOON" message or the "SERVICE NOW" message will appear on the Driver Information Center (DIC). Some codes may not cause "ENGINE CONTROL SYSTEM" light to illuminate. Light may go out automatically if malfunction clears.
If malfunction is intermittent, the "ENGINE CONTROL SYSTEM" light will go out when malfunction is no longer detected. Light will come on each time malfunction is detected. When a "SERVICE SOON" malfunction is detected at the same time a "SERVICE NOW" malfunction is detected, only the "SERVICE NOW" message will be displayed. The "ENGINE CONTROL SYSTEM" light stays on when system is in self-diagnostic mode.
Intermittent & Hard Codes
A hard or "CURRENT" failure code is one that was detected the last time the ECM tested the circuit in the current key on cycle. When a hard or "CURRENT" failure is detected, the appropriate telltale light and DIC service message are displayed.
A "HISTORY" or intermittent failure code is one that was detected at some time in the last 50 key on cycles. The failure will remain in ECM memory as an intermittent or "HISTORY" code until the ECM detects the failure again or the code is cleared.
BCM/ECM COMPUTER SYSTEM STATUS LIGHT DESCRIPTIONS
While in the diagnostic mode, indicators on the CCDIC are used to indicate status of certain operating modes. Different modes of operation are indicated by status light being turned on or off.
"AUTO" Status Indicator
This indicator is turned on whenever the ECM is operating in closed loop fuel control. Light should come on after the coolant and oxygen sensors have reached normal operating temperatures.
"ECON" Status Indicator
This indicator is turned on whenever the oxygen sensor signal to the ECM indicates a rich exhaust condition. Light should switch between rich and lean (flash on and off) during warm, steady throttle operation.
"°C" Status Indicator
This indicator is turned on whenever the ECM senses that the vehicle is in 3rd gear. The 3rd gear switch switch is opened by 3rd gear oil pressure, illuminating the indicator. Indicator will turn off when vehicle is not in 3rd gear.
"°F" Status Indicator
This indicator is turned on whenever the ECM senses that the vehicle is in 3rd and 4th gear. The 3rd and 4th gear pressure switched are opened by 3rd and 4th gear oil pressure, illuminating the indicator. Indicator will turn off whenever vehicle is not in 3rd or 4th gear.
"°E" Status Indicator
This indicator is turned on whenever the ECM senses that the vehicle is in 4th gear without the 3rd gear pressure switch having been opened. indicator will turn off when vehicle is not in 3rd or 4th gear.
"FRONT DEFOG" Status Indicator
This indicator is turned on whenever the BCM is commanding the A/C compressor clutch to engage. (Scheme 3) Light indicates whether the clutch is enabled or disabled by the BCM. Actual operation depends on integrity of A/C-heater system and wiring.
"REAR DEFOG" Status Indicator
This indicator is turned on whenever the ECM is commanding the Viscous Converter Clutch (VCC) to engage. The light only indicates whether the VCC is enabled or disabled by the ECM. Actual operation depends on integrity of VCC system and wiring.
"LO" Status Indicator
This indicator is turned on whenever the ECM senses the throttle switch is closed. Indicator is turned off whenever the ECM senses the throttle switch is open.
"NORM" Status Indicator
This indicator is turned on whenever the ECM senses the vehicle is in Park or Neutral (switch closed). Indicator is turned off whenever the ECM senses vehicle is not in Park or Neutral (switch open).
ECM DATA DISPLAYS IDENTIFICATION
When trouble shooting a malfunction, the ECM and BCM data display can be used to compare problem vehicle with a vehicle that is functioning properly. The following is a brief summary of each parameter.
ECM "ED01" Data Code
The Throttle Position Sensor (TPS) position will be displayed in degrees.
ECM "ED02" Data Code
Manifold Air Pressure (MAP) sensor reading is displayed in Kilopascals (kPa).
ECM "ED03" Data Code
The computed barometric pressure will be displayed in Kilopascals (kPa).
ECM "ED04" Data Code
The coolant temperature is displayed in degrees Celsius (°C). (Scheme 3)
ECM "ED05" Data Code
Manifold Air Temperature (MAT) sensor reading is displayed in degrees Celsius (°C).
ECM "ED06" Data Code
Injector pulse width is displayed in milliseconds (ms).
ECM "ED07" Data Code
Oxygen sensor reading is displayed in volts.
ECM "ED08" Data Code
Spark advance is displayed in degrees. (Scheme 3)
ECM "ED10" Data Code
Battery state of charge is displayed in volts.
ECM "ED11" Data Code
Engine speed is displayed in RPM.
ECM "ED12" Data Code
Vehicle speed is displayed in MPH.
ECM "ED18" Data Code
Oxygen (O2) sensor cross-counts are displayed as the number of times the O2 sensor crossed reference line each second. (Scheme 3)
ECM "ED19" Data Code
Fuel integrator operation is displayed in counts.
ECM "ED26" Data Code
The transmission temperature will be displayed in degrees Celsius (°C).
ECM "ED70" Data Code
Cruise control servo operation is displayed in percent. A value close to "0" represents the at rest position. A value close to "100" represents wide open throttle.
ECM "ED98" Data Code
The ignition cycle counter value is the number of times the ignition key is cycled to the "OFF" position since an ECM trouble code was last detected. After 50 ignition cycles without any malfunction being detected, all stored ECM codes are cleared. (Scheme 3)
ECM "ED99" Data Code
The ECM Programmable Read-Only Memory (PROM) identification number is displayed as a number up to 3 digits long which can be used to verify that proper PROM is installed in ECM.
BCM "BD20" Data Code
The commanded A/C-heater system blower motor voltage is read in volts.
BCM "BD21" Data Code
Coolant temperature is displayed in degrees Celsius (°C). Value is sent from ECM to BCM. If circuit malfunctions, as determined by ECM, the ECM will send a failsoft value for display.
BCM "BD22" Data Code
The commanded A/C-heater system air-mix door position is displayed in percent. A value close to "0" represents a cold air-mix. A value close to "100" represents a warm (heated) air-mix.
BCM "BD23" Data Code
Actual A/C-heater system air-mix door position is displayed in percent. This value should closely follow commanded air position, except when door is commanded beyond its mechanical limit of travel.
BCM "BD24" Data Code
The A/C-heater system air delivery mode is displayed as a number from "0" to "7". Each number is a code which represents an air delivery mode. See AIR DELIVERY CODE IDENTIFICATION table.
| Code Number | Air Delivery Mode |
|---|---|
| "0" | Maximum A/C |
| "1" | Normal A/C |
| "2" | Intermediate |
| "3" | Heater |
| "4" | Off |
| "5" | Normal Purge |
| "6" | Cold Purge |
| "7" | Defrost |
AIR DELIVERY CODE IDENTIFICATION
BCM "BD25" Data Code
In-car temperature sensor reading is displayed in degrees Celsius (°C).
BCM "BD26" Data Code
Actual outside (ambient) temperature is displayed in degrees Celsius (°C). This value represents actual ambient temperature sensor reading and is not restricted by features used to minimize engine heat effects on display value.
BCM "BD27" Data Code
The A/C high-side temperature (condenser output) is displayed in degrees Celsius (°C).
BCM "BD28" Data Code
The A/C low-side temperature (evaporator input) is displayed in degrees Celsius (°C).
BCM "BD32" Data Code
The A/C-heater system sunload temperature sensor reading is displayed in degrees Celsius (°C).
BCM "BD40" Data Code
Actual fuel level is read in gallons. Value represents actual sensor position and is not restricted by the features used to eliminate fuel slosh effects on display value.
BCM "BD41" Data Code
The "PRND321" (transmission gear position) is displayed in a 4-digit binary number for each gear position. See GEAR POSITION CODE IDENTIFICATION table.
| Gear Position | Code Number |
|---|---|
| "P" | 0110 |
| "R" | 0011 |
| "N" | 1010 |
| "D" | 1001 |
| "3" | 0000 |
| "2" | 0101 |
| "1" | 1100 |
GEAR POSITION CODE IDENTIFICATION
BCM "BD42" Data Code
The dimming pot value is displayed in percent. A value close to "0" represents daylight. A value close to "100" represents maximum brightness.
BCM "BD43" Data Code
Twilight delay pot value displays in percent. Value close to "0" represents daylight. A value close to "100" represents darkness.
BCM "BD44" Data Code
Twilight photocell value is displayed in percent. Value close to "0" represents daylight. Value close to "100" represents darkness.
BCM "BD50" Data Code
Battery state of charge is displayed in volts.
BCM "BD51" Data Code
Alternator field value is displayed in percent. A value close to "0" represents minimum regulator on time. A value close to "100" represents maximum regulator on time.
BCM "BD60" Data Code
Vehicle speed is displayed in MPH.
BCM "BD61" Data Code
Engine speed is displayed in RPM.
BCM "BD90" Data Code
Options display a number representing installed vehicle option. See VEHICLE OPTION CODE IDENTIFICATION table.
| Code Number | Option |
|---|---|
| "0" | 2-Door |
| "1" | 4-Door |
| "128" | 2-Door French/Canadian |
| "129" | 4-Door French/Canadian |
VEHICLE OPTION CODE IDENTIFICATION
BCM "BD91" Data Code
Option 2 displays "---" since no related options exist.
BCM "BD98" Data Code
The ignition cycle counter value is the number of times the BCM has been turned off since a BCM trouble code was last detected. After 100 ignition cycles without any malfunction being detected, all stored BCM codes are cleared.
BCM "BD99" Data Code
The BCM Programmable Read-Only Memory (PROM) identification number is displayed as a 4-digit number.
ECM Diagnostics/Basic Operation & Status Light Displays. Scheme 3
ECM Diagnostics/Data,Input,Output Tests/Fixed Spark Mode. Scheme 4
INPUT DISPLAYS
When trouble shooting a malfunction, the ECM, BCM, or IPC input display can be used to determine if the 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 the input terminal voltage for that circuit.
The display also indicates if the input changed state (activated or deactivated) since it was last tested. If a change occurred, an "X" will appear next to the "HI"/"LO" indicator. If a change did not occur, an "O" will remain displayed. The "X" will only appear once per selected input.
Input display may show Instrument Panel Cluster (IPC) trouble codes. IPC input codes are prefixed with an "II" (Instrument Input). The following is a brief summary of each ECM, BCM and IPC input.
ECM "EI71" Input Code
The brake switch display is "LO" when brake pedal is depressed. (Scheme 4)
ECM "EI72" Input Code
The throttle switch display is "HI" when accelerator pedal is depressed.
ECM "EI74" Input Code
The park/neutral switch display is "LO" when vehicle is in Park or Neutral.
ECM "EI78" Input Code
The power steering pressure switch display is "LO" when power steering pressure (effort) is high. (Scheme 4)
ECM "EI79" Input Code
The cruise control "ON/OFF" switch display is "HI" when switch is in the "ON" position.
ECM "EI80" Input Code
The cruise control "SET/COAST" switch display is "HI" when "ON/OFF" switch is in the "ON" position and the "SET/COAST" switch is depressed.
ECM "EI81" Input Code
The cruise control "RESUME/ACCEL" switch display is "HI" when "ON/OFF" switch is in the "ON" position and the "RESUME/ACCEL" switch is pushed. (Scheme 4)
BCM "BI01" Input Code
The courtesy light panel switch display is "LO" when courtesy lights are turned on from switch.
BCM "BI02" Input Code
The parking light switch display is "LO" when parking light switch is in the "OFF" position.
BCM "BI03" Input Code
The driver's door (front door on Seville) ajar switch display is "LO" when the driver's (front) door is ajar (open).
BCM "BI04" Input Code
The passenger's door (rear door on Seville) ajar switch display is "LO" when the passenger's (rear) door is ajar (open).
BCM "BI05" Input Code
The door jamb switch display is "LO" when any door is open.
BCM "BI06" Input Code
The door handle switch display is momentarily "LO" when either front outside door handle button is depressed.
BCM "BI07" Input Code
The trunk open switch display is "LO" when trunk is open.
BCM "BI08" Input Code
The A/C low refrigerant pressure switch display is "LO" when system is low on refrigerant.
BCM "BI09" Input Code
The windshield washer fluid level switch display is "LO" when vehicle is low on washer fluid.
BCM "BI10" Input Code
"LO COOLANT" not used in 1988 Eldorado and Seville.
BCM "BI30" Input Code
Temp/time switch display is "LO" when button is depressed.
BCM "BI41" Input Code
The cooling fan feedback display is "LO" when cooling fans are running.
BCM "BI51" Input Code
The alternator feedback display is "LO" when there is an alternator problem or engine is not running.
IPC "II78" Input Code
Headlight switch display is "HI" whenever headlights are on.
IPC "II79" Input Code
The high beam switch display is "LO" as long as lever is pulled in.
IPC "II80" Input Code
The dimming sentinel switch display is "LO" whenever system is turned on.
IPC "II81" Input Code
The dimming sentinel switch photosensor display is "HI" whenever it senses light.
IPC "II82" Input Code
Twilight enable switch display is "LO" whenever system is on.
OUTPUT DISPLAYS
When trouble shooting a malfunction, ECM and BCM output test can be actuated regardless of inputs and normal program instructions. Once a test in outputs is selected, the test will display "HI" or "LO" for 3 seconds in each state to indicate the command and output terminal voltage. The following is a brief summary of each output.
ECM "EO00" Output Code
This test displays "CYCLE NONE" message as no outputs are activated at this point.
ECM "EO01" Output Code
The canister purge solenoid display will be "LO" when solenoid is energized.
ECM "EO02" Output Code
The Viscous Converter Clutch (VCC) display will be "LO" when VCC solenoid is energized.
ECM "EO03" Output Code
The EGR solenoid display will be "LO" when solenoid is energized.
ECM "EO04" Output Code
The AIR management system air switching solenoid display will be "LO" when solenoid is energized.
ECM "EO05" Output Code
The AIR management system air diverter solenoid display will be "LO" when solenoid is energized.
ECM "EO06" Output Code
The ISC motor display will be "LO" when plunger is retracting and "HI" during plunger extension.
ECM "EO07" Output Code
The cruise control vent solenoid display is "HI" when vent solenoid is energized. The cruise control "ON/OFF" switch must be on and the engine off for this output to cycle.
ECM "EO08" Output Code
The cruise control vacuum solenoid display is "HI" when vacuum solenoid is energized. The cruise control "ON/OFF" switch must be on and the engine off for this output to cycle.
ECM "EO09" Output Code
The A/C relay display will be "HI" when relay is energized.
ECM "EO99" Output Code
All of the previously mentioned outputs are cycled simultaneously. The "HI" and "LO" corresponds to status indications previously described.
BCM "BO00" Output Code
The "CYCLE NONE" display will not display "HI" or "LO" as this is a resting spot where no outputs will be cycled.
BCM "BO03" Output Code
The Retained Accessory Power (RAP) relay display is "LO" when relays are energized.
BCM "BO04" Output Code
Courtesy light relay display is "LO" when relay is energized.
BCM "BO05" Output Code
Twilight relays display is "LO" when relays are energized.
BCM "BO06" Output Code
The "HI/LO" beam headlight relays display is "LO" when relays are energized.
OVERRIDE DISPLAYS
When trouble shooting a malfunction, the override feature allows testing of certain system functions regardless of normal program instructions. Upon selecting a test that functions, that selection's current operation will be represented as a percentage of its full range. This value will be displayed on the CCDIC panel.
The display will alternate between "--" for one second, followed by the normal program value for 10 seconds. This alternating display is a reminder that function is not currently being overridden.
Pressing the "WARMER" or "COOLER" buttons on the CCDIC begins the override, at which time the display will no longer alternate to "--". When in override, pressing the "WARMER" button increases the value, while pressing the "COOLER" button decreases the value.
Upon release of button, the display may remain in either the override value or return to normal program control. If display remains at the override value, normal program control can be resumed in one of 3 different ways
- Selection of another override test will cancel the current override.
- Selection of another system will cancel the current override.
- Overriding the value beyond either extreme (0 or 99) will display "--" momentarily and then jump to the opposite extreme. If the button is released while "--" is being displayed, normal program control will resume and the display will again alternate.
The override test type is unique in that any other test type within the selected system may be activated at the same time. After selecting an override test, pressing the "OFF" button will allow selection of another test type, yet the CCDIC will continue to display the selected override. By selecting another test type, while at the same time pressing the "WARMER" or "COOLER" buttons, it is possible to monitor the effect of the override on different vehicle parameters.
ECM "ES00" Override Code
This test will display a "NONE" message as no overrides are active at this point.
ECM "ES01" Override Code
The viscous converter clutch solenoid override can be activated by the "WARMER" or "COOLER" buttons. Its status is displayed as "ON/OFF".
ECM "ES02" Override Code
The EGR solenoid override status is displayed as "ON/OFF". Due to use of a positive backpressure type EGR valve, this test will have no significance at idle.
ECM "ES03" Override Code
ISC motor override status is displayed as "UP/DN" (up/down).
ECM "ES04" Override Code
The cruise control servo override status is displayed as "UP/DN" (up/down).
BCM "BS00" Override Code
This test will display a "NONE" message as no overrides are active at this point.
BCM "BS01" Override Code
The program number override can be controlled from "0" (maximum A/C) to "98" (maximum heating). The display will hold the override value upon release of "WARMER" or "COOLER" button.
BCM "BS02" Override Code
The vacuum fluorescent dimming override can be controlled from "0" (maximum dimming) to "99" (maximum brightness). Display will hold the override value upon release of "WARMER" or "COOLER" button.
BCM "BS03" Override Code
The incandescent bulb dimming override can be controlled from "0" (maximum dimming) to "99" (maximum brightness) if parking lights are turned on. The display will hold the override value upon release of "WARMER" or "COOLER" button.
BCM "BS04" Override Code
The cooling fans override can be controlled from "0" (fans off) to "99" (maximum cooling fan operation) as long as the button is held. Normal control will resume upon release of the "WARMER" or "COOLER" button.
FIXED SPARK MODE (SETTING IGNITION TIMING)
- Initial base timing is set by jumpering pins "A" and "B" together at ALDL connector, while NOT in diagnostic mode. The ALDL connector is located near brake pedal, just below dash. (Scheme 5)
- Set timing to specification shown on EMISSION CONTROL LABEL. Jumpering pins "A" and "B" together will cause a "SET TIMING" message to appear on CCDIC. This indicates that ECM is in set ignition timing mode.
ALDL Connector. Scheme 5
WIRING DIAGRAMS
Note. Wiring diagram not available. For system schematic (Scheme 1)
See also:
• AIR DELIVERY CODE IDENTIFICATION