3800 VIN [c] - BCM Tests W/codes Oldsmobile Toronado IV

PRELIMINARY PROCEDURES

Prior to any hard part diagnosis, various system checks should be performed.

1. Check to see if "Service Engine Soon" light is working. If this light fails to light when the ignition is turned on and engine is not running, problem could be in power supply circuits to these systems. The "Self-Diagnostic Check" will direct you to the appropriate diagnostic chart.
2. Can "Service Mode" be accessed? If CRT is not operable, self-diagnostics are not possible. In this case, the "Self-Diagnostic System Check" will direct you to the appropriate diagnostic chart.
3. Are there any service code(s) displayed? If a trouble code is identified using self-diagnostics, a problem has been detected by the system which can be corrected by following the appropriately numbered fault code. Codes with the prefix "E", are ECM codes. Codes with the prefix "B", are BCM codes.
4. Perform a visual check of the entire system. Check the suspected wiring and components. Inspect hoses that are difficult to see beneath the compressor, generator, etc. Inspect all related wiring for opens, improper connections, burned or chafed spots, pinched wires, contact with sharp edges or contact with hot exhaust manifolds.

Trouble Codes

During the process of controlling various subsystems, the ECM and BCM continually monitor operating conditions for possible system malfunctions. By comparing system conditions against standard operating limits, certain circuit and component malfunctions can be detected.

A 3-digit numerical "Trouble Code" is stored in computer memory when a problem is detected. These trouble codes can later be displayed to aid technician in diagnosing the system. This display of diagnostic trouble codes can only be accessed in the "Service Mode".

Certain system malfunctions cause computer controlled diagnostic messages and/or telltales to appear, indicating that service is required. When a subsystem circuit exceeds preprogrammed limits, a system malfunction is indicated and the BCM provides certain back-up functions known as "Failsoft". A typical "Failsoft" action would be the substitution of a fixed input value when a sensor is detected to be open or shorted.

ENTERING "SERVICE MODE"

Note. Operating vehicle in the "Service Mode" for extended time periods (1/2 hour or longer), without the engine running, will cause battery drain, and possibly relate false diagnostic information and/or a no-start condition.

Turn ignition switch to "ON" position. Touch "OFF" and "WARM" buttons on ECC control panel simultaneously, and hold until a segment check is displayed on the instrument panel and ECC control panel (usually about 3 seconds). (Scheme 1)

Electronic Climate Control (ECC) Panel (Toronado). Scheme 1

CLIMATE CONTROL IN SERVICE MODE

When in the "Service Mode", the climate control will continue to operate in whatever setting it was in prior to the "Service Mode". Even though the display may change as the buttons are touched, the previous operating mode is remembered and will resume after entering "Service Mode".

After trouble codes have been displayed, the "Diagnostic 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, the first available system will be displayed (i.e. ECM). While selecting a system to test, any of the following actions may be taken to control the display

1. Pressing the "OFF" button will stop the system selection process and return the display to the beginning of trouble code sequence.
2. Pressing the "LOW" fan button will display the next available system selection. This allows all system selections to be displayed. The list of systems can be repeated following the display of the last system.
3. Pressing the "HIGH" fan button will select the displayed system for testing. At this point the first available test type will appear with the selected system above it.
4. Pressing the "BI-LEVEL" button will exit diagnostics and return to normal IPC and ECC operation.

TEST TYPE SELECTION

Having selected a system, the first available test type will be displayed (i.e. "ECM DATA"). When selecting a specific test type the following are available actions to be taken

1. Pressing the "OFF" button will stop the test type selection process and return to the next available selection.
2. Pressing the "LOW" fan button will display the next available test type for the selected system. This allows all available test types to be displayed for selection.
3. Pressing the "HIGH" fan button will select the displayed test type. At this point the display will either indicate whether the selected test type is in progress, or the first of several tests will appear.
4. Pressing the "BI-LEVEL" button will exit diagnostics.

TEST SELECTION

Selection of the "DATA", "INPUTS", or "OUTPUTS" test types will result in the first available test being displayed. If "==" message appears, this test is not allowed with the engine running. Turn engine off and repeat sequence.

The last 4 characters of the display will contain a test code to identify the selection. The first 2 of these characters are letters which identify the system and the test type (i.e. ED for ECM DATA) and last 2 characters numerically identify the test (i.e. ED01 for Throttle Position). When selecting a specific, the following actions may be taken to control the display

1. Pressing the "OFF" button will stop the test selection process and return the display to the next available test type for the selected system.
2. Pressing the "LOW" fan button will display the next smaller test number for the selected test type. If this button is touched with the lowest test number displayed, the highest test number will then appear.
3. Pressing the "HI" fan button will display the next larger test number for the selected test type. If this pad is touched with the highest test number displayed, the lowest test number will then appear.

Toronado Service Mode Operation Sequence. Scheme 2

Upon selecting an "OVERRIDE" test function, current operation will be represented as a percentage of its full range. This value will be displayed on the ECC panel. The display will alternate between "-" and the normal program value. This alternating display is a reminder that function is not currently being overridden.

Pressing the "WARM" or "COOL" buttons on the ECC panel begins the override, at which time the display will no longer alternate to "-". Pressing the "WARM" button increases the value, while pressing the "COOL" button decreases the value. Normal program control can be resumed in one of 3 ways.

1. Selection of another override test will cancel the current override.
2. Selection of another system (ECM, BCM or IPC) will cancel the current override.
3. 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 begin alternating.

The override test type is unique in that any other test type within the selected system may be active at the same time. After selecting an override test, pressing the "OFF" button will allow selection of another test type (DATA, INPUTS or OUTPUTS). The ECC panel will continue to display the selected override. By selecting another test type and test, while at the same time pressing the "WARM" or "COOL" button, it is possible to monitor the effect of the override on different vehicle parameters.

CODE RESET SELECTION

Selecting the reset codes will result in the message "CLEAR ECM CODES?" or "CLEAR BCM CODES?", depending on which system was being tested. At this point, the following action may be taken

1. Pressing the "OFF" button will stop the test selection process and return the display to the next available test type for the selected system.
2. Pressing the "LO" fan button will display the next test type.
3. Pressing the "HI" fan button will select "CLEAR CODES". A message "ECM CODES CLEARED" or "BCM CODES CLEARED" will appear to indicate those codes have been cleared from memory.
4. Pressing the "BI-LEV" button will exit diagnostics.

ECM Snapshot

Selection of "SNAPSHOT?" test type while in the ECM system level, will result in the message "SNAPSHOT TAKEN" being displayed with the selected system name preceding it. This message will appear for 3 seconds to indicate that all ECM data and inputs have been stored in memory. After 3 seconds, the display will proceed to the first available snapshot test type, "SNAP DATA?". While selecting a snapshot test type, any of the following actions may be taken to control the display

1. Pressing the "OFF" button on the ECC panel will stop the test type selection process and return the display to the next available system selection.
2. Pressing the "LO" button will display the next available snapshot test type. This allows the display to be stepped through all available choices. This list of snapshot test types can be repeated following the display of the last choice.
3. Pressing the "HI" button with "SNAP DATA?" or "SNAP INPUTS?" displayed will select that test type. At this point the display is controlled as it would be for non-snapshot data and input displays, however, all values and status information represents memorized vehicle conditions.
4. Pressing the "HI" button with "SNAPSHOT?" displayed, will again display the "SNAPSHOT TAKEN" message to indicate that new information has been stored in memory. Access to this information is obtained the same as previously described.

BCM Snapshot

Selection of "SNAPSHOT?" test type while in the BCM system level will allow the recall of up to 3 snapshots recorded at the time, of the setting of BCM malfunction codes. Also, one may trigger the recording of a snapshot upon demand. Selecting snapshot (pushing the "HI" button) while in the BCM system, will result in the display of "BXXX". The "XXX" is the 3 digit diagnostic code that recorded the snapshot. While selecting snapshot, any of the following actions may be taken to control the display

1. Pressing the "OFF" button on the ECC panel will stop the test type selection process and return the display to the next available system selection.
2. Pressing the "LO" button will allow scrolling through the list of BCM diagnostic codes that the BCM has stored a snapshot for. After the last BCM diagnostic code, (or the third if there are more than 3 codes set) pressing the "LO" button will return to the first "BXXX SNAP?" display.
3. Pressing the "HI" button with "SNAP DATA?" or "SNAP INPUTS?" displayed, will select that test type. At this point the display is controlled as it would be for non-snapshot data and input displays, however, all values and status information represents memorized vehicle conditions.

IPC SEGMENT CHECK

When the ignition is on and the "SYSTEM MONITOR" button is pressed, the BCM will cause the IPC and ECC to sequentially illuminate and darken all segments and lights in the clusters. This helps to determine if any bulbs or segments of the instrument cluster vacuum fluorescent display are out, or always on. Also, to give the technician more time to study the various segments, whenever service diagnostics are entered, a total illumination of all segments and bulbs on the IPC and ECC will also occur.

EXITING "SERVICE MODE"

To exit the "Service Mode", press the "BI-LEV" button. Trouble codes are not erased when this is done. Any mode button will exit diagnostics, however, the "BI-LEV" button was chosen for consistency.

DATA DISPLAYS

When trouble shooting a malfunction, the ECM and BCM data display can be used to compare the problem vehicle, with a vehicle that is functioning properly. The following is a brief summary of each parameter.

BCM DATA DISPLAY CODES

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.

Also, the display indicates if the input changed state 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.

BCM INPUT DISPLAY CODES

IPC INPUT DISPLAY CODES

OUTPUT DISPLAYS

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

BCM OUTPUT DISPLAY CODES

OVERRIDE DISPLAYS

When trouble shooting a malfunction, the BCM override feature allows testing of certain system functions regardless of normal program instructions.

The override feature, or test type, is unique in that any other test type within the selected system may be active at the same time.

BCM OVERRIDE DISPLAY CODES

TROUBLE CODE DISPLAY

After the "Service Mode" is entered, any trouble codes stored in the computer will be displayed. ECM codes will be displayed first. If no ECM codes are stored, the IPC will display "NO ECM CODES". All ECM codes will be prefixed by an "E" (i.e. EO13).

When all ECM codes have been displayed, BCM codes will be displayed. BCM codes mainly deal with body control functions, with climate control being one of its main features. BCM codes are prefixed with an "B" (i.e. B110). BCM codes can also be accompanied by "Current", indicating that the fault still exists. If no BCM codes exist, "NO BCM CODES" message will be displayed.

Both ECM and BCM codes are displayed in 2 second intervals starting at the lowest numbered code and ending at the highest. If the "LO" fan button is pressed anytime during the display of ECM and BCM codes, the display of codes will be by-passed. If at any time the "BI-LEVEL" button is pressed, the BCM will exit the "Service Mode" and go back to normal vehicle operation.

BCM TROUBLE CODES

CODE B110, OUTSIDE TEMPERATURE SENSOR CIRCUIT

The outside air temperature sensor is a thermistor that controls the signal voltage to the BCM. The BCM applies and monitors voltage on circuit No. 735 to the sensor. When the sensor is cold, its resistance is high, therefore the BCM will see a high monitored voltage. As the sensor warms, its resistance becomes less and the signal voltage is pulled low through the sensor ground, circuit No. 736. This signal voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

Code B110 will set if the ignition is on and the signal voltage indicates less than -31°F (-35°C), which is open circuit voltage or greater than 137°F (58°C), which is shorted circuit voltage. During the time the failure is present, a substitute temperature reading will used to allow continued operation of the climate control system, and the continuous compressor at idle will be disabled. The outside air temperature reading BD26 will however, display the actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD26 displays outside temperature. The normal range is from -31°F (-35°C) to 137°F (58°C).
2. Checks to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminals, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.
4. Checks to see if the shorted circuit reading is due to the circuit or the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are okay.

Note On Intermittents

If the ambient temperature drops below about -31°F (-35°C), this code should be ignored.

If an intermittent Code B110 is being set, manipulate the related wiring while observing BCM data BD26. If the failure is induced, the reading will jump from its normal value to a reading outside the range of -31°F (-35°C) to 137°F (58°C).

If the value displayed by BD26 is not reasonably close to the actual temperature of the air at the sensor, check for poor terminal contact or replace sensor.

Code B110, Outside Temperature Sensor Circuit. Scheme 3

CODE B111, A/C HIGH SIDE TEMPERATURE SENSOR CIRCUIT

The A/C high side temperature sensor is a thermistor that controls the signal voltage to the BCM. The BCM applies and monitors voltage on circuit No. 732 to the sensor. When the sensor is cold, its resistance is high, therefore, the BCM will see a high monitored voltage. As the sensor warms, resistance becomes less and the signal voltage is pulled low through the sensor ground, circuit No. 736. This monitored voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

Code B111 will set if the ignition is on, the outside temperature sensor has not failed and reads greater than 32°F (0°C), and the signal voltage indicates less than -24°F (33°C), which is open circuit voltage or over 408°F (209°C), which is shorted circuit voltage. During the time the failure is present, a substitute temperature reading will be used to allow continued operation of the climate control system. The A/C high side temperature reading BD27 will, however, display the actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD27 displays A/C high side temperature. The normal range is from -27°F (-33°C) to 408°F (209°C).
2. Checks to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminal, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.
4. Checks to see if the shorted circuit reading is due to the circuit or the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are okay.

If an intermittent Code B111 is being set, manipulate the related wiring while observing BCM data BD27. If the failure is induced, the reading will jump from its normal value to a reading outside the range of -24°F (-33°C) to 409°F (209°C).

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

A/C High Side Temperature Sensor Circuit. Scheme 4

CODE B112, A/C LOW SIDE TEMPERATURE SENSOR CIRCUIT

The A/C low side temperature sensor is a thermistor that controls the signal voltage to the BCM. The BCM applies and monitors voltage on circuit No. 731 to the sensor. When the sensor is cold, its resistance is high, therefore, the BCM will see a high monitored voltage. As the sensor warms, its resistance becomes less and the signal voltage is pulled low through the sensor ground, circuit No. 736. This monitored voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

Code B112 will set if the ignition is on, the outside temperature sensor has not failed and reads greater than 32°F (0°C), and the signal voltage indicates less than -29°F (-34°C), which is open circuit voltage or greater than 209°F (85°C), which is shorted circuit voltage. During the time the failure is present, a substitute temperature reading (the same value as outside air temperature) will be used to allow continued operation of the climate control system and the compressor clutch will be disabled. The A/C low side temperature reading BD28 will, however, display the actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD28 displays A/C low side temperature. The normal range is from -29°F (-34°C) to 209°F (85°C).
2. Checks to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminals, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.
4. Checks to see if the shorted circuit reading is due to the circuit or the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are okay.

If an intermittent Code B112 is being set, manipulate the related wiring while observing BCM data BD28. If the failure is induced, the reading will jump from its normal value to a reading outside the range of -34°F (-29°C) to 209°F (85°C).

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

Code B112, A/C Low Side Temperature Sensor Circuit. Scheme 5

CODE B113, IN-CAR TEMPERATURE SENSOR CIRCUIT

The in-car temperature sensor is a thermistor that controls the signal voltage to the BCM. The BCM applies and monitors voltage on circuit No. 734 to the sensor. When the sensor is cold, its resistance is high, therefore, the BCM will see a high monitored voltage. As the sensor warms, its resistance becomes less and the monitored voltage is pulled low through the sensor ground, circuit No. 736. This signal voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

Code B113 will set if the ignition is on, the outside temperature sensor has not failed and reads greater than 32°F (0°C), and the signal voltage indicates less than -29°F (-34°C), which is open circuit voltage or greater than 209°F (85°C), which is shorted circuit voltage. During the time the failure is present, a substitute temperature reading will be used to allow continued operation of the climate control system. The in-car temperature reading BD25 will, however, display the actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD25 displays in-car temperature. The normal range is from -29°F (-34°C) to 209°F (85°C).
2. Checks to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminals, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.
4. Checks to see if the shorted circuit reading is due to the circuit or the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are okay.

If an intermittent Code B113 is being set, manipulate the related wiring while observing BCM data BD25. If the failure is induced, the reading will jump from its normal value to a reading outside the range of -29°F (-34°) to 209°F (85°C).

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

Code B113, In-Car Temperature Sensor Circuit. Scheme 6

CODE B115, SUN LOAD SENSOR CIRCUIT

The sun load sensor is a thermistor that controls the signal voltage to the BCM. The BCM applies and monitors voltage on circuit No. 590 to the sensor. When the sensor is cold, its resistance is high, therefore, the BCM will see a high monitored voltage. As the sensor warms, its resistance becomes less and the monitored voltage is pulled low through the sensor ground, circuit No. 736. This monitored voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

Code B115 will set if the ignition is on, the outside temperature sensor has not failed and reads greater than 32°F (0°C), and the signal voltage indicates less than -29°F (-34°C), which is open circuit voltage, or over 209°F (85°C), which is shorted circuit voltage. During the time the failure is present, a substitute temperature reading will be used to allow continued operation of the climate control system. The sun load temperature reading BD32 will, however, display the actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD32 displays sun load temperature. The normal range is from -29°F (-34°C) to 209°F (85°F).
2. Checks to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminals, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.
4. Checks to see if the shorted circuit reading is due to the circuit or the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are okay.

If an intermittent Code B115 is being set, manipulate the related wiring while observing BCM data BD32. If the failure is induced, the reading will jump from its normal value to a reading outside the range of -29°F (-34°) to 209°F (85°C).

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

Code B115, Sun Load Sensor Circuit. Scheme 7

CODE B119, TWILIGHT PHOTOCELL CIRCUIT

Note. Be sure nothing is covering sensor before following this procedure.

The twilight sensor uses a photocell to control the signal voltage to the BCM. The BCM applies and monitors voltage on circuit No. 278 to the sensor. When the sensor detects darkness, its resistance is high, therefore, the BCM will see a high monitored voltage. As the sensor detects light, its resistance becomes less and the monitored voltage is pulled low through the ground, circuit No. 736. This signal voltage will vary between 5 volts (open circuit) and zero volts (shorted circuit).

Code B119 will set if the ignition is on and the signal voltage indicates more than 98 percent, open circuit voltage or less than 2 percent, which is shorted circuit voltage). During the time the failure is present, a substitute light reading (indicating darkness) will be used to allow continued operation of the headlights. The measure of light reading (BD44), however, will display the actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD44 displays light level. The normal range is from 2-98 percent.
2. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminals, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.
4. Checks to see if the shorted circuit reading is due to the circuit or the sensor. If the shorted circuit reading changes to an open circuit reading after disconnecting the sensor, the BCM and wiring are okay.

If an intermittent Code B119 is being set, manipulate the related wiring while observing BCM data parameter BD44. If the failure is induced, the reading will jump from its normal value to a reading outside the range of 2-98 percent. Make certain owner is aware not to cover sensor.

Code B119, Twilight Photocell Circuit. Scheme 8

CODE B120, TWILIGHT DELAY SWITCH POT CIRCUIT

The twilight delay uses a potentiometer to control the signal voltage to the BCM. The BCM supplies and monitors voltage on circuit No. 705 to the resistor in the left switch assembly and returns as a ground to the BCM on circuit No. 736. The wiper provides the voltage signal to the BCM on circuit No. 271, indicating position of the slider and delay time. When the slider is moved toward the maximum position (maximum delay), resistance is low, the BCM will see a high monitored voltage on circuit No. 271. As the slider is moved toward the minimum position (minimum delay), resistance increases and the monitored voltage decreases. This signal voltage will vary between zero volts (open or grounded circuit) and 5 volts (shorted to voltage circuit). BD43 displays a low percentage for minimum delay and a high percentage for maximum delay of headlight "on" time.

Code B120 will set if the ignition is on and the signal voltage indicates less than 2 percent (open or grounded circuit) or greater than 98 percent (shorted to voltage). During the time the failure is present, a substitute delay time (minimum delay) will be used to allow continued operation of the twilight system. The reading from the potentiometer BD43, however, will display the actual reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD43 displays twilight delay time. The normal range is 2-98 percent.
2. Checks to see if the open or grounded circuit reading is due to the circuit or the switch. If the open or grounded circuit reading changes from a short to voltage reading after jumping the switch assembly terminals, the BCM and wiring are okay.
3. Measuring between circuit No. 705 (5 volts) and circuit No. 271 will determine if circuit No. 271 is open or shorted to ground.
4. Checks to see if the short to voltage circuit reading is due to the circuit or the switch assembly. If a short to voltage reading changes to an open circuit reading after disconnecting the switch assembly, the BCM and wiring are okay.

If an intermittent Code B120 is being set, manipulate the related wiring while observing BCM data parameter BD43. If the failure is induced, the reading will jump from its normal value to a reading outside the range of 2-98 percent.

Code B120, Twilight Delay Switch Pot Circuit. Scheme 9

CODE B120 & B122, TWILIGHT DELAY & PANEL DIMMING

Because both potentiometers use the same power and ground, chances are that the problem is in the power or ground circuits when both codes are stored.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD43 displays twilight delay time. The normal range is 2-98 percent.
2. Checks to see if the open or grounded circuit reading is due to the circuits or switch assembly. If voltage can be read across circuits No. 705 and 736 after disconnecting the switch assembly, the BCM and wiring are okay.
3. Checks for 5-volt reference at the switch. If 5 volts is present, circuit No. 736 is open. If circuit No. 736 is open, the open will be between terminal No. 4 on left switch assembly and splice "A".
4. If circuit No. 705 is suspected of being grounded, remove the HVAC programmer and BCM connectors prior to making a ground check.
5. If there is no ground in circuit No. 705, replace HVAC programmer or BCM.

If intermittent Codes B120 and B122 are being set, manipulate the related wiring while observing either BCM data parameter BD42 and/or BD43. If the failure is induced, the reading will jump from its normal value to a reading outside its range (see specific chart for range).

Code B120 & B122, Twilight Delay & Panel Dimming. Scheme 10

CODE B122, PANEL DIMMING SWITCH POT CIRCUIT

The panel dimmer uses a potentiometer to control the signal voltage to the BCM. The BCM supplies and monitors voltage on circuit No. 705 to the resistor in the left switch assembly and returns as a ground to the BCM on circuit No. 736. The wiper provides the voltage signal to the BCM on circuit No. 686, indicating position of the slider and dim level. When the slider is moved toward the maximum position (bright), resistance is high, therefore the BCM will see a low monitored voltage. As the slider is moved toward the minimum position (dim), its resistance decreases and monitored voltage increases. This signal voltage will vary between zero volts (open or grounded circuit) and 5 volts (shorted to voltage circuit). BD42 displays a low percentage for dim and a high percentage for bright panel illumination.

Code B122 will set if the ignition is on and the signal voltage indicates less than 2 percent (open or grounded circuit) or greater than 98 percent (shorted to voltage). During the time the failure is present, a substitute dimming value will be used to allow continued operation of interior lighting. The reading from the potentiometer BD42, however, will display the actual reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD42 displays the amount of panel dimming. The normal range is 2-98 percent.
2. Checks to see if the open or grounded circuit reading is due to the circuit or the switch assembly. If the open or grounded circuit reading changes from a short to voltage reading after jumping the switch assembly terminals, the BCM and wiring are okay.
3. Measuring voltage between circuit No. 705 (5 volts) and circuit No. 686 will determine if circuit No. 686 is open or shorted to ground.
4. Checks to see if the short to voltage circuit reading is due to the circuit or the switch assembly. If a short to voltage reading changes to an open circuit reading after disconnecting the switch assembly, the BCM and wiring are okay.

If an intermittent Code B122 is being set, manipulate the related wiring while observing BCM data parameter BD42. If the failure is induced, the reading will jump from its normal value to a reading outside the range of 2-98 percent.

Code B122, Panel Dimming Switch Pot Circuit. Scheme 11

CODE B123, COURTESY LIGHTS SWITCH CIRCUIT (TORONADO)

The panel lights switch uses the same physical control as the dimming pot. Inside the left switch assembly, the panel lamp switch contacts close when the dimming slider is moved to its extreme maximum position (on). The BCM supplies a voltage on circuit No. 685 to the switch. When the slider is moved to the extreme maximum position (on), the switch contacts close and the signal voltage is pulled low. This will turn on the courtesy lights.

Code B123 indicates that the BCM terminal "2A5" was pulled to ground but the dimmer switch position was less than a value for maximum panel light brightness. A grounded circuit No. 685 will not only set Code B123, but will also turn the courtesy lights on at all times and run the battery down.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM input value BI01 displays the voltage state of the circuit at the BCM. These conditions can be observed in BCM input display BI01 as readings of "HIGH " or "LOW" when the dimming slider is moved. "HIGH" indicates circuit is not grounded and lights should be off.
2. By removing the switch assembly, a shorted switch can be detected by observing B101.
3. By removing the BCM connector, the short to ground can be isolated as being the wire or the BCM.

If circuit No. 685 was intermittently grounded, Code B123 could be stored. Manipulate circuit No. 685 while observing BI01 with the dimmer at a low setting. If the short occurs, the value will switch from "HIGH" to "LOW".

Also check BCM data BD42. Cycle panel dimming control from minimum to maximum. If BD42 does not range between 2-98 percent, or never reads more than 75 percent, then replace left switch assembly.

Code B123, Courtesy Lights Switch Circuit. Scheme 12

CODE B124, VEHICLE SPEED SENSOR (VSS) CIRCUIT PROBLEM

The vehicle speed sensor uses a Permanent Magnet (PM) generator to generate an electrical signal representative of vehicle speed. This signal is brought to the BCM by circuit No. 400 (VSS high) and circuit No. 401 (VSS low), where the BCM buffers and amplifies the signal for its prospective uses. Output of the generator can be seen by using a digital voltmeter on the AC scale while rotating the generator drive (rotate front wheels).

Code B124 will set under the following conditions

1. Ignition on.
2. No Codes EO29, EO31 or B334.
3. Transaxle in 4th gear (EI82 "LOW")
4. No input to the BCM from the VSS.
5. Engine speed greater than 800 RPM.

During the time the failure is present, the continuous compressor at idle will be disabled, however, vehicle speed reading BD60 will display actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. Since the BCM amplifies and buffers the speed signal before it is sent to the ECM, Code EO24 in the ECM will set along with Code B124 in the BCM if the PM generator or circuits No. 400 and 401 have a problem. If Code B124 ever sets without setting a Code EO24, there is an internal problem in the BCM.
2. BCM data value BD60 displays MPH.
3. With the wheels turning, a voltage reading indicates that the PM generator and wiring are okay.
4. Checks for open in VSS circuit wiring.
5. Checks for ground in VSS circuit wiring prior to replacing sensor.

If an intermittent Code B124 is being set, manipulate the related wiring while observing BCM data parameter BD60. If the failure is induced, the reading will jump from a normal value to zero MPH.

Code B124, Vehicle Speed Sensor, Circuit Problem. Scheme 13

CODE B127, GEAR SELECTOR SWITCH CIRCUIT

The gear selector switch is mounted on the transaxle assembly. It is a multi-signal switch sending information relative to gear selector position to the BCM and ECM. The switch assembly also contains the neutral safety switch and back-up light switch, and provides park input to the automatic door lock module (if equipped). The switch uses 4 discrete circuits to pull 4 BCM terminal voltages low in various combinations to indicate each gear range. The voltage level of each of the circuits is represented in BCM data BD41. "0" = low, "1" = high. The 4 digits displayed represent decoder A, B, C and parity inputs in sequence.

The switch also provides park/neutral inputs to the ECM in a similar manner using one discrete input. This can be seen using ECM input EI74, where "HI" or "LO" represent the voltage level of input terminal. Code B127 will set if the following conditions occur

1. BCM gear selector switch input indicates P/N but ECM input does not.
2. BCM gear selector switch input does not indicate P/N but ECM input does.
3. Decoder and parity inputs do not agree with possible combinations.

If Code B127 is set, the DIC will display the warning message "GEAR SELECT PROBLEM" and IPC gear position display (PRND21) will flash.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks BCM inputs when only decoder A and parity circuit are pulled low.
2. Checks BCM inputs when only decoder B and C inputs are pulled low. This will complete high/low check of all 4 BCM inputs.
3. This step is to check gear selector switch problem in other gear ranges.
4. Checks to see if code is due to discrepancy between ECM and BCM inputs.
5. Checks for short to ground in gear selector switch to BCM circuits.
6. Checks for open in gear selector switch to BCM circuits.
7. Circuit shorted to ground will result in a "0" for the circuit.
8. Checks for open gear selector sensor ground.
9. Circuit with open will result in a "1" for the circuit.

Manipulate related ECM and BCM wiring in each gear range while looking for a change in BD41 or EI74 values to check for intermittent open or short to ground. Also check terminals for good contact at ECM, BCM and gear selector switch. If good contact exists and Code B127 continues to set, replace BCM.

Code B127, Gear Selector Switch Circuit (1 of 2). Scheme 14

Code B127, Gear Selector Switch Circuit (2 of 2). Scheme 15

CODE B132, ENGINE OIL PRESSURE SENSOR CIRCUIT FAULTY

The oil pressure indicator uses a variable resistor to control the signal voltage at the BCM. The BCM supplies and monitors a 5-volt signal on circuit No. 313 to the sensor. When the engine is not running (oil pressure low), sensor resistance is low and the signal voltage drops low when it returns through circuit No. 736. When the engine is running (increased oil pressure), sensor resistance becomes greater and monitored voltage is high on circuit No. 313.

Code B132 will set if the monitored voltage indicates oil pressure greater than 252 psi (18 kg/cm 2 ). As actual engine oil pressure will never be that high, the code indicates an open circuit, faulty sensor or faulty BCM.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD71 displays oil pressure. The normal range is from 0-80 psi.
2. Checks to see if the open circuit reading is due to the circuit or the sensor. If the open circuit reading changes to a shorted circuit reading after jumping the sensor terminals, the BCM and wiring are okay.
3. By applying a ground to various points in the circuits, an open can be isolated by observing whether the parameter display can be changed from the open reading to the shorted reading.

If an intermittent Code B132 is being set, manipulate the related wiring while observing BCM data parameter BD71. If the failure is induced, the reading will jump from zero to some oil pressure above 80 psi with the engine off.

Engine Oil Pressure Sensor Circuit Faulty. Scheme 16

CODE 140, PHONE SYSTEM PROBLEM (OPTIONAL)

Code B140 will set if the ignition is on and PWM signal on circuit No. 901 to the BCM is indicating Mode 7 (BCM Data Display BD45). This code will also set if the CRTC does not get a message back from the phone over the E & C data bus when you try to turn power on or off, or try to lock the phone from the CRT.

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if there is a data bus problem or just a phone problem.
2. Determines if the code set is due to the phones hardware signal to the BCM or because of communication problem.
3. Since the phone should work on its own as the CRTC is just an alternative way of dialing, try to work the phone from the handset. This will determine if the phone is the problem or if there is a data bus problem isolating the CRTC from the phone.

Note. Cellular telephone requires service or repair.

Code B140, Phone System Problem (Optional). Scheme 17

CODE B332, LOSS OF COMPASS MODULE DATA

Code B332 will set if the BCM cannot communication with the compass module for longer than 2 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. Since the data circuit to the compass is spliced off the data loop, an open in circuit No. 800X will not stop the BCM from communicating with any of the other devices. However, if Code B337 is set, data from the BCM may not be getting to the programmer.
2. Determines is the code is intermittent.
3. Checks to see if the compass module has power and ground.
4. Determines if it is the 7 volt circuit or ground that is open.
5. Determines is the data circuit is open or if the compass module is bad.

If Code B332 shows up as "History", check for intermittent opens in circuits No. 801E, 807C and/or 800X. The problem will not be a short in these circuits as this would prevent on-board diagnostics from operating.

Code B332, Loss Of Compass Module Data. Scheme 18

CODE B334, LOSS OF ECM SERIAL DATA

Code B334 will set if communication between the ECM and the BCM is lost. If the BCM remains powered and only serial communication is lost, the vehicle will still run, but with the ignition key on (engine not running), a "LOW OIL PRESSURE" message will be displayed followed by an "ELECTRICAL PROBLEM" message about 25 seconds later.

Note. Test numbers refer to numbers on diagnostic chart.

1. If the ECM loses power or ground, the code will set because the ECM cannot communicate, but the key here is that the engine will not start.
2. Checks for serial data at the ECM. Normally voltage should be greater than one volt and varying. The normal 1-5 volts varying only indicates there are no opens up to the ECM.
3. If the code resets and since the prior checks eliminated an open circuit, the fault is poor terminal contact at ECM terminal "A8", or a faulty ECM.

If an intermittent Code B334 is being set, manipulate the related wiring at the ECM. With the ignition key on (engine not running), a "LOW OIL PRESSURE" message will indicate loss of ECM communication, and possibly help to isolate the intermittent without having to look for the code.

Code B334, Loss of ECM Serial Data. Scheme 19

CODE B336, LOSS OF IPC SERIAL DATA

This code can only be viewed as a "HISTORY" code because if it was current, service diagnostics could not be entered. Since serial data (+7 volts) and ground terminals are redundant, it would take a double open in any of those circuits to set the code. A single intermittent open in circuit No. 343 would also set the code.

If codes are intermittent, careful checking of all terminal contacts is required prior to any parts being replaced.

If IPC presently has a loss of serial data, diagnostics cannot be displayed. Current faults are covered on charts B-1 or B-2.

Code B336 indicates an intermittent has occurred. Should intermittent problem persist, check the following circuits for opens or poor terminal contacts.

CIRCUIT-TO-IPC TERMINAL IDENTIFICATION

Also check circuits No 800B and 800C, including good terminal contact at terminals "C4" and "D4". If intermittent persists, replace IPC. When all diagnosis and repairs are completed, clear codes and verify operation.

Code B336, Loss Of IPC Serial Data. Scheme 20

CODE B337, LOSS OF HVAC PROGRAMMER DATA

Code B337 will set if the ignition is on and the BCM is not able to exchange data with the programmer. This can occur if the HVAC loses ignition, ground, or both serial data circuits.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for power and ground up to the programmer. The test light should be on when connected from ignition source to both grounds.
2. Since power and ground are available to the programmer, the source for failure is either a double open in the circuit No. 800 or faulty terminal contacts.

Code B337 Schematic, Loss Of HVAC Programmer Data. Scheme 21

Code B337 Flow Chart, Loss Of HVAC Programmer Data. Scheme 22

CODE B410, CHARGING SYSTEM CIRCUIT

The generator on this vehicle has fault detection capability built into the regulator. The BCM supplies 12 volts on circuit No. 25 and monitors the field voltage on circuit No. 23.

Code B410 will set if the following occur

1. An open or short to ground in circuits No. 23 or 25.
2. Drive belt breakage.
3. Overvoltage or undervoltage.

Circuit No. 25 will normally carry 12 volts from the BCM to the generator in order to continuously signal the regulator. A short to ground on circuit No. 25 will cause the generator to not work, a Code B409 to set, the "NO CHARGE" telltale will light on the IPC and the "GENERATOR PROBLEM" message will be displayed on the DIC.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM input BI51 displays generator signal voltage as "HIGH" or "LOW", depending on the voltage state at the BCM. Normally, with key on and engine off, circuit No. 25 voltage will be pulled low by the generator and BI51 will read "LOW".
2. Checks to see if "LOW" reading is due to circuit No. 25 or the generator. If display reading changes from "LOW" to "HIGH" when the generator is disconnected with engine running, the BCM and circuit No. 25.
3. Checks to see if the "LOW" reading is due to the BCM or circuit No. 25.
4. BCM data value BD51 displays the amount of generator field activity. Under normal conditions, a reading less than 7 percent would indicate a fault in the field circuit at the BCM.
5. Removing the generator connector will determine if the fault is due to the generator or an open in circuit No. 25, including the BCM and interface connector.

Perform a comprehensive visual check of the generator wiring and connections.

Code B410, Charging System Circuit. Scheme 23

CODE B411 OR B412 BATTERY VOLTAGE TO LOW OR TOO HIGH

Code B411 will set, when the ignition is on, and the engine RPM is greater than 800, and BCM is seeing an ignition one fuel reference voltage of less than 10.5 volts. B412 will set under the same conditions if voltage is more than 16 volts. During the time the failure is present, the cruise control will be disengaged. When the code sets, the charging system problem page appears. This code should be fixed first, as low or high voltage could cause false readings and prevent any codes from setting.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD50 displays battery voltage. The normal range is 10.5-16 volts.
2. Checks to see if the low or high voltage readings are due to the circuit, the battery and/or the generator. With the engine running, if voltage is below 10.5 volts or above 16 volts, the BCM and wiring are okay.
3. Checks to see if the low voltage reading is due to the circuit or the BCM. If the voltage at the BCM is below 10.5 volts, then the BCM is okay.
4. Checks to see if generator is faulty under load conditions.

If an intermittent Code B411 or B112 is being set, observe BCM data parameter BD50. This battery voltage reading is monitored off of the 10 amp isolation ignition 1 fuse, fuel reference voltage. If the code is being set, due to an high current draw in a certain vehicle component, this can be observed by reading the display for BD50. Operate the various components, while watching for the reading to fall outside the range of 10.5-16 volts.

B411 & B412, Battery Voltage Too Low Or Too High. Scheme 24

CODE B420, TWILIGHT LIGHT RELAY CIRCUITS

The BCM operates the twilight and courtesy light relays by providing a ground for the coils. When the relay(s) are on, the BCM output will be low, and when the relay(s) are off, the BCM output will be high. Code 420 will set if the ignition is on and the output voltage at the BCM is not what has been commanded.

Note. Test numbers refer to numbers on diagnostic chart.

1. To determine which system has failed (courtesy lights or twilight), select the BCM output function in diagnostic mode. As the individual outputs cycle on and off, observe their actual operation.

Since both sets of relays can cause an intermittent condition, see NOTE ON INTERMITTENTS in chart B420 (2 of 3) and (3 of 3).

Code B420, Twilight Relay Circuits (1 of 3). Scheme 25

CODE B420, COURTESY LIGHT RELAY CIRCUIT

If the courtesy lights did not cycle on and off when BO04 was selected, then this is the relay that set Code B420.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if the fault is due to an open circuit or short to ground in the circuit. If the courtesy lights are always on, there is a short to ground in the control circuit. If the courtesy lights are never on, there is an open in on of the circuits.
2. Checks to see if the sort to ground is due to the circuits or the BCM.
3. Checks to see if the open circuit is due to the circuit or the BCM.
4. Checks to see if the open circuit is on the power side of the relay.
5. Checks to see if the open circuit is on the ground side of the relay or if the relay is faulty.

If an intermittent Code B420 is being set, manipulate the related wiring in output mode and watch for relays to cycle.

Code B420, Courtesy Light Relay Circuit (2 of 3). Scheme 26

CODE B420, TWILIGHT RELAYS CIRCUIT

If the headlight and parking lights did not cycle on and off when BO05 was selected, then this is the system that set Code B420

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if the fault is due to an open circuit or a short to ground in the circuit. If the headlights and parking lights are always on, there is a short to ground in control circuit. If the headlights and parking lights never turn on, there is an open in one of the circuits.
2. Checks to see if the sort to ground is due to the circuit or BCM.
3. Checks to see if the open circuit is due to the circuit or BCM.
4. Checks to see if the open circuit is on the power or ground side of the relay.

If an intermittent Code B420 is being set, manipulate the related wiring in output mode and watch for relays to cycle.

Code B420, Twilight Relays Circuit (3 of 3). Scheme 27

CODE B440, HVAC - AIR MIX DOOR CIRCUIT PROBLEM

Code B440 is set by the BCM if it is unable to move the air mix door. The BCM requests the door to move over the data circuit No. 800 to the programmer. With the ignition on, the programmer supplies voltage (5 volts from BCM circuit No. 705) to the motor that drives the air mix door. The BCM monitors a feedback potentiometer on the DC motor which varies between zero and 5 volts depending on its position. If the door is requested to move, but the feedback voltage does not change, the BCM stores Code B440 to indicate that the door is not responding to its command. If the air mix door feedback indicates it is near the hot or cold extreme, the code will not set if it is commanded to move to that extreme.

Operation of the air mix door can be evaluated in BCM data display by observing actual air mix door position (BD23 "ACT MIX DR") while changing the program number (override BS01 "PROGRAM NO").

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD23 displays actual air mix door position. The normal range is 1-99 percent. The BCM override value BS01 is for the program number. As the program number is changed from zero (maximum A/C) to 99 (maximum heat), the door position should vary between its mechanical limits of travel.
2. Checks to see if the fault could be to the 5-volt reference and ground circuit or the sensor circuit.
3. Checks to see if the fault is due to the programmer or the sensor circuit.
4. Checks to see if the fault is due to the circuit or the BCM.

If an intermittent Code B440 is being set, manipulate the related wiring while observing actual air mix door position (BD23 movement. If the failure is induced, the door position will either stop or jump to an extreme value (Zero or 100 percent). This will help in isolating the location of the malfunction.

Exit diagnostics. Select "MAX HEAT" (90°) and "MAX COOL"(60°) using normal HVAC controls, waiting a minimum of 2 minutes in each mode to see if code sets.

Code B440, HVAC - Air Mix Door Circuit Problem. Scheme 28

CODES B446, B447 & B448 LOW REFRIGERANT PRESSURE

In the process of controlling the compressor clutch, the BCM monitors certain system inputs for an indication of low refrigerant charge. If the system refrigerant state of charge should fall below about 1/3 its capacity, the BCM is capable of detecting this condition and will display a driver warning message to warn the operator. The BCM determines the state of charge by its low side temperature sensor and the low refrigerant pressure switch. Since temperature and pressure are proportionally related in the A/C system, a low temperature is the same as low pressure. In addition to the message, the BCM will store a Code B446, B447, or B448 in memory to indicate that a low refrigerant condition was detected.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM input value BI08 displays the voltage state of the circuit at the BCM.
2. Checks to see if the open circuit reading is due to the circuit or the switch.
3. Checks to see if the fault is on the ignition side or the BCM side of the switch circuit.
4. This step checks to see if the fault is due to the pressure switch or a low refrigerant charge.

Low Refrigerant Pressure (1 of 2). Scheme 29

It has been determined from the previous chart that the problem is not in the low refrigerant pressure switch circuit.

Note. Test numbers refer to numbers on diagnostic chart.

1. This is a test to determine if the A/C low refrigerant pressure switch opens while the compressor is running. If BI08 remains "HIGH" during compressor engagement, then the system fault is due to the refrigerant. Service A/C system.
2. This checks if the switch is opening due to a low refrigerant pressure charge or the switch.

Note. Perform appropriate A/C system diagnosis.

Low Refrigerant Pressure (2 of 2). Scheme 30

CODE B449, HVAC - HIGH SIDE TEMPERATURE TOO HIGH

Code B449 is designed to disengage the A/C compressor clutch in the event that high side refrigerant temperature exceeds 199°F (93°C). The A/C compressor will come back on once the high side temperature falls below 195°F (87°C).

If the code was stored or current temperature exceeds 199°F (93°C), possible causes for excessive high A/C head pressure must be checked. Perform a refrigerant system performance test.

1. Key on, engine running with A/C on
2. Select BCM data BD27 A/C high side temperature °F (°C)
3. Note temperature displayed during A./C operation

CODE B450, HVAC - COOLANT TEMPERATURE TOO HIGH

Code B450 is designed to disengage the A/C compressor clutch if the engine coolant temperature exceeds 261°F (127°C) and re-engage when temperature falls below 248°F (120°C).

1. Engine running, enter diagnostics.
2. Select BCM data BD21, coolant temperature °F (°C).
3. Note coolant temperature.

Engine overheating may accompany this code. If coolant temperature exceeds normal operating range, check for sources of overheating. Carefully check all sources of intermittent engine overheating, such as improper cooling fan operation, faulty belt or belt tension, coolant level, and restrictions or faulty hoses or routings. If coolant temperature displayed exceeds actual coolant temperature, as measured with a radiator coolant temperature testing device, the sensor may be faulty.

CODE B482, ANTI-LOCK BRAKE PRESSURE PROBLEM

This code indicates that the brake pressure switch has indicated a low pressure condition to the BCM. Code B482 sets whenever circuit No. 933 is pulled low to ground and stays low for 50 seconds. As soon as voltage goes low, the Red brake telltale will come on. The warning message on the DIC for "LOW BRAKE PRESSURE" will not come up until after 50 seconds, at the same time the code sets. The Amber anti-lock telltale in the IPC is controlled only by the ABS unit.

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if fault is present.
2. Determines if fault is due to circuit problem or actual ABS brake system problem.

If switch status reads "HI" when 5-pin hydraulic switch connector is unplugged, fault is not in circuit. This is a ABS malfunction.

If this code is set as "HISTORY" and you are not experiencing braking problems, look for a sort to ground in circuit No. 933. Shorted condition would have to be present at least 50 seconds.

Code B482, Anti-Lock Brake Pressure Problem. Scheme 31

CODE B552, BCM KEEP ALIVE MEMORY ERROR

Code B552 does not normally indicate a fault, but is a normal occurrence anytime the power to the BCM has been interrupted. Code B552 cannot be cleared from memory in the normal manner. Code B552 can only be cleared if it is not "CURRENT". Under normal conditions, the code will become "HISTORY", by the following: key in "LOCK", wait 5 seconds, turn key on, and then reenter diagnostics. This code should now be "HISTORY", and can be cleared in the normal manner.

The code will also set if the following conditions are met: ignition in "Crank" and no system voltage signal to BCM terminal "1C9". The purpose of the crank circuit is to signal the BCM to shut off when cranking so that voltage variations that are normal during starting do not affect the electronic devices.

This code could also set during cranking if the system voltage drops below 8 volts at BCM terminal "1C9". Possible causes for this are: faulty charging system, faulty starter system, extreme cold weather and/or jump starting the vehicle.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step is to change Code B552 from "CURRENT" to "HISTORY".
2. Checks to see if Code B552 was set due to a fault in the crank signal circuit.
3. By removing the fuel pump fuse, the engine will not start and voltage during cranking can be observed.
4. Checks for sufficient system voltage at BCM terminal "1C9". System voltage must not drop below 8 volts during cranking.
5. If the fuse is blown, check for a ground in circuit No. 806. A blown fuse will appear the same at the BCM as an open in circuit No. 806.

Code B552 indicates that the keep alive/or "LONG TERM" memory in the BCM has been reset. This will be the case whenever power is removed from the BCM (such as, disconnecting the battery cables, disconnecting BCM power connector, or losing crank signal to the BCM). This code should be cleared from memory after restoring the BCM power supply.

Code B552, Keep Alive Memory Error. Scheme 32

CODE B556, ODOMETER EEPROM ERROR

Code B556 indicates that the EEPROM,which records elapsed odometer mileage, is not being read by the BCM. Usually along with

Code B556, "ERROR" will be displayed in the odometer display.

1. Check for proper EEPROM installation.
2. If PROM is properly installed, no bent pins, then replace EEPROM. NOTE: New EEPROM will have to be adjusted to the current mileage, proper VIN, and option content by the authorized AC-DELCO service center.
3. If a properly installed EEPROM continues to display "ERROR", replace BCM.

Code B556, Odometer EEPROM Error. Scheme 33

CODE B660, CRUISE CONTROL NOT IN DRIVE

Code B660 will set if the cruise control is engaged and the BCM receives a gear selector position signal indication that the vehicle is in Park, Reverse, or Neutral. During the time the failure is present, the BCM will disengage the cruise control system.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD41 displays gear selector position as a percentage value. The insert on Code B660 chart compares gear selector position with BD41 value.
2. BD41 may display very low values if switch is misadjusted to be between gears.

This code was designed to prevent cruise control operation when the vehicle is not in a forward gear. This code can e set if the operator selects Neutral, when the cruise control is engaged. This will cause the cruise to drop out until the operator reengages the cruise. If the operator describes this condition, but did not move the gear selector out of the forward gears, check adjustment of the gear selector switch, or for looseness in the switch mounting, or connections that could cause intermittent signal to the BCM.

Code B660, Schematic. Scheme 34

Code B660, Cruise Control Not In Drive. Scheme 35

CODE B663, CRUISE SPEED DIFFERENCE BETWEEN ACTUAL AND SET IS TOO LARGE

Code B663 will set and disengage the cruise control if the actual speed is 30 MPH higher or lower than the set speed. This code is used to set upper and lower limits for operation of the cruise control system, and can be set under normal conditions if the operator accelerates, using the gas pedal, and goes 30 MPH over the set speed. If the operator experiences cruise drop out with this code set, but did not accelerate 30 MPH over the set speed, a mechanical problem is indicated.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM override value BS05 displays commanded servo position. The commanded range is normally 0-99 percent. If the servo will not go to full stroke, the vacuum supply, servo, or vacuum brake release circuit is leaking
2. Checks to see if vacuum leak is due to brake release valve and circuit, or servo and source vacuum.
3. Checks to see if vacuum leak is due to vacuum source or servo.
4. Checks to see if fault is due to intermittent or slow vacuum leak.
5. Checks to see if fault is servo or brake vacuum release circuit.

If code B663 is setting intermittently, make sure owner is not overrunning set speed by more than 30 MPH. Check vacuum source and brake release vacuum lines for proper connections or slow leaks.

Cruise Speed Diff. Between Actual & Set Too Large. Scheme 36

CODE B664, CRUISE ACCELERATION TOO HIGH

If any codes higher than B664 are also set, go to that code(s) first.

This code will set and disengage the cruise control if vehicle acceleration exceeds a preset rate, calibrated in the BCM (16 MPH/Sec.).

This could occur on slippery pavement, or during a long downhill acceleration. This could also occur for some mechanical problems such as transmission slippage. Under these condition, code setting is normal and driver should be advised.

Clear the codes and road test vehicle to verify normal operation.

CODE B667, SET/COAST OR RESUME/ACCEL CIRCUIT SHORTED

"When the cruise control "ON/OFF" switch and ignition are on, system voltage is available at one side of the normally open contacts on the "Set/Coast" and "Resume/Accel" switches. If the cruise control "ON/OFF" switch was turned to "ON" position, system voltage will be available to the "Set/Coast" or "Resume/Accel" switches at key in "ON" position. If the "Set/Coast" and "Resume/Accel" switches were stuck, or their signal wires to the BCM were shorted to voltage, the vehicle could begin cruise operation. To prevent this, Code B667 will set and disable cruise control, if the signal voltage from the "Set/Coast" (circuit No. 84) or the "Resume/Accel" (circuit No. 87) is high when the cruise control "ON/OFF" switch is turned from "OFF" to "ON", or with ignition switch turned to "ON" position and the cruise control "ON/OFF" switch was left in the "ON" position. Cruise control will be disabled until the BCM sees a low on both of these signals.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM inputs BI76 and BI77 display "Set/Coast" and "Resume/Accel" switch status as "HIGH" or "LOW" depending on the voltage state at the BCM. If one of these inputs stays "HIGH" when the switches are cycled, that particular switch or signal wore is shorted to voltage.
2. Checks to see if short circuit reading is due to switch or circuit.

If an intermittent Code B667 is being set, manipulate the related wiring while observing BCM inputs BI76 and BI77. If the failure is induced, the reading will jump from "LOW" to "HIGH" with the switch off (not depressed). This code can also be set by the operator if the cruise "ON/OFF" switch is turned on and the operator was depressing either the "Set/Coast" or "Resume/Accel" switches.

Set/Coast Or Resume/Accel Circuit Shorted. Scheme 37

CODE B671, CRUISE - SERVO POSITION SENSOR CIRCUIT PROBLEM

Code B671 will set if the ignition is on and the servo position sensor signal is below 3 percent. During the time the failure is present, the cruise control will be disengaged.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM data value BD70 displays servo position. The normal range is above 3 percent.
2. Checks to see if fault is due to short or open in the feedback circuits.
3. Checks to see if open circuit reading is due to servo or circuits.
4. Checks to see if problem is intermittent. BD70 will not go as low or as high as BS05 because of its mechanical limits of travel; however, it should never go less than 3 percent.

If an intermittent Code B671 is being set, manipulate the related wiring while observing BCM data BD70. If the failure is induced, the reading will jump from its normal value to a reading below 3 percent.

Cruise - Servo Position Sensor Circuit Problem. Scheme 38

CODE B672, CRUISE - VENT SOLENOID CIRCUIT PROBLEM

The cruise control vent solenoid receives a rapidly switched voltage signal from the BCM to control the amount of time the solenoid is energized. During the time the output is "HIGH", the solenoid is energized and vacuum is not vented (or it is trapped) from the servo.

Code B672 will set if the cruise is on, the brake is not depressed, and the BCM output is "HIGH" when it should be "LOW" , or "LOW" when it should be "HIGH". Under these conditions, the BCM will disable the cruise control until the BCM sees the proper output signal. These determinations are made on the circuitry internal to the BCM and may not affect the "HIGH" or "LOW" displayed during "Service Mode", as they only indicate where the BCM wants the output signal and not what it is actually at. An output display of "LOW" means circuit No. 403 should be de-energized (vent solenoid off) and an output display of "HIGH" means circuit No. 403 should be energized (vent solenoid on). Circuit No. 403 will be "HIGH" when the solenoid is energized, as the BCM is providing voltage to the vent solenoid which has its own full-time ground. Circuit No. 403 will be "LOW" when the solenoid is de-energized, as the BCM takes away the voltage feed to the solenoid.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM output BO01 cycles the vent solenoid. The "HIGH" and "LOW" refer to the state of the voltage at the BCM
2. Checks to see if fault is due to servo or circuit.
3. Checks to see if fault is due to open ground circuit or control circuit, including servo solenoid.
4. Checks to see if fault is shorted servo or control circuit.

If an intermittent Code B672 is being set, manipulate the related wiring while in the output function BO01 and listen for the solenoid to cycle, or stop cycling. This will have to be done slowly, as this function cycles the solenoid on and off every 3 seconds. DO NOT be fooled into thinking the spot has been found, as it could be the end of the 3 second interval. Make sure the intermittent condition can be induced a few times.

Cruise - Vent Solenoid Circuit Problem. Scheme 39

CODE B673, CRUISE - VACUUM SOLENOID CIRCUIT PROBLEM

The cruise control vacuum solenoid receives a rapidly switched voltage signal from the BCM to control the amount of time the solenoid is energized. During the time the output is "HIGH", the solenoid is energized and vacuum is supplied to the servo.

Code B673 will set if the cruise is on, the brake is not depressed, and the BCM output is "HIGH" when it should be "LOW", or "LOW" when it should be "HIGH". Under these conditions, the BCM will disable the cruise control until the BCM sees the proper output signal. These determinations are made on the circuitry internal to the BCM and may not affect the "HIGH" or "LOW" displayed during "Service Mode", as they only indicate where the BCM wants the output signal and not what it is actually at. An output display of "LOW" means circuit No. 402 should be de-energized (vacuum solenoid off) and an output display of "HIGH" means circuit No. 402 should be energized (vacuum solenoid on). Circuit No. 402 will be "HIGH" when the solenoid is energized, as the BCM is providing voltage to the vent solenoid which has its own full-time ground. Circuit No. 402 will "LOW" when the solenoid is de-energized, as the BCM takes away the voltage feed to the solenoid.

Note. Test numbers refer to numbers on diagnostic chart.

1. BCM output BO02 cycles the vacuum solenoid. The "HIGH" and "LOW" refer to the state of the voltage at the BCM
2. Checks to see if fault is due to servo or circuit.
3. Checks to see if fault is due to open ground circuit or control circuit, including servo solenoid.
4. Checks to see if fault is shorted servo or control circuit. If the vacuum solenoid is shorted (less than 25 ohms), BCM replacement will also be necessary.

If an intermittent Code B673 is being set, manipulate the related wiring while in the output function BO02 and listen for the solenoid to cycle, or stop cycling. This will have to be done slowly, as this function cycles the solenoid on and off every 3 seconds. DO NOT be fooled into thinking the spot has been found, as it could be the end of the 3 second interval. Make sure the intermittent condition can be induced a few times.

Cruise - Vacuum Solenoid Circuit Problem. Scheme 40

CODE C553, CRTC KEEP ALIVE MEMORY ERROR

Code C553 indicates that the keep alive, or long term memory in the CRTC has been reset. This will be the case whenever power is removed from the CRTC (such as, disconnecting the battery cables). This code should be cleared from memory after restoring the CRTC power supply. If this code continually sets without a Code B552, check circuit No. 805 (crank input to CRTC) for an open. If not open, make a complete check of battery state of charge and condition, as this code is more sensitive than Code B552. A shorted cell in the battery may result in this code setting. CRTC keep alive memory is the memory for radio, such as preset stations, volume, and balance settings. It is also the memory for personal message storage.

CHART B-1, LOSS OF SERIAL DATA

The IPC indicates a loss of serial data communication by displaying only the message "ELECTRICAL PROBLEM". All other segments are blank. If the display is fully illuminated and an "ELECTRICAL PROBLEM" message is also displayed, enter diagnostics and proceed to the appropriate code chart. DO NOT use Chart B-1. Loss of serial data can occur because there is a short to voltage or ground in circuit No. 800, a double open in circuit No. 800, a loss of 7-volt supply which powers serial communication or an internal BCM/IPC fault.

Note. Test numbers refer to numbers on diagnostic chart.

1. The serial data fault can be isolated to circuit No. 800 if dashes are displayed, a loss of ground at the ECC panel if a segment check is displayed or an open to or in the IPC if the ECC is okay.
2. This step defines what type of fault is on circuit No. 800. Normal serial communication produces 1-4 volts varying along the circuit.
3. If low voltage is found, this step distinguishes between a grounded circuit or a loss of 7 volts, since loss of serial data will not keep the courtesy lights from functioning, but a loss of 7 volts will.

Chart B-1, Loss Of Serial Data. Scheme 41

CHART B-2, LOSS OF IPC DISPLAY

A loss of IPC display and messages may be a result of the following

1. Loss of battery voltage to the IPC.
2. Loss of ground to the IPC.
3. Loss of 7 volts to the IPC.
4. Ground in 7-volt circuit No. 807, anywhere along its length.
5. Internal BCM or IPC fault.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks for ignition source to IPC. Normally, there will be battery voltage at terminal "D2" with the key on.
2. This step checks for CPS ignition source and ground to the IPC.
3. This step checks for 7-volt source to the IPC. Since the 7-volt circuit is shared by several components, this test isolates the area or type of 7-volt loss.

Chart B-2, Loss Of IPC Display. Scheme 42

CHART B-2A, CPS CHECK

The central power supply (CPS) provides a conditional or filtered 12 volts, 7 volts and a ground for most of the major computers in the system. The BCM is continuously supplied 12 volts from the CPS. When a "Wake-Up" signal, such as opening a door or turning the ignition switch "ON" is received by the BCM, a 12-volt signal is sent from the BCM to the CPS to turn on the 7-volt supply. The 7 volts powers the circuits in the various computers that control the serial data communications.

The CPS requires a constant 12-volt supply from the CPS fuse and a ground to operate. The BCM must supply the "Wake-Up" signal to activate the 7-volt supply in the CPS.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks for a 12-volt supply and a ground to the CPS.
2. This step checks for a "Wake-Up" signal back to the CPS. If the test light is on, the "Wake-Up" signal is occurring and the fault is in the 7-volt circuit. No light indicates that the "Wake-Up" signal is not occurring.
3. This step checks for 12 volts into the BCM and a "Wake-Up" signal out of the BCM.
4. This step checks for source of ignition "3" at the BCM. Ignition "3" is a source of the "Wake-Up" signal.
5. This step checks for the source of the short by testing all the 12-volt circuits and components on those circuits for a short to ground. If the 12-volt circuits are okay, then the fault is in circuit No. 640 or a faulty fuse.

Chart B-2A, CPS Check. Scheme 43

CHART B-3

This chart should be used when the IPC displays only "ELECTRICAL PROBLEM" and the ECC has a normal display of temperature. This can occur if the IPC loses serial data or 7-volt supply, or an internal IPC fault occurs.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks for serial data voltage. Voltage should be more than one volt and varying.
2. This step checks for 7-volt supply to the IPC. While only one 7-volt terminal is necessary for the IPC to function, both circuits should be complete.
3. If the serial data and 7 volts is available at the connector, the fault is either poor connections at those terminals or an internal IPC fault.
4. With less than one volt at the IPC connector, there is an open in the serial data circuit. Normal voltage should be more than one volt and varying.

Chart B-3. Scheme 44

CHART B-4, GROUNDED SERIAL DATA CIRCUIT

With a grounded serial data circuit, the BCM will not be able to communicate with the other devices in the system. Voltage measured anywhere along the circuit will be near zero. The only display on the IPC is "ELECTRICAL PROBLEM".

Note. Test numbers refer to numbers on diagnostic chart.

1. This step splits the system in half to help isolate the source of the grounded serial data line. If taking the chime/voice module out of the system allows both halves of the serial data line to rise to more than one volt, the source of the short was the module.
2. The remaining steps follow the same pattern, in that the components are removed from the serial data line until the normal voltage range is measured. When the section of the circuit is isolated, a simple check of the wire for a short to ground differentiates between a grounded wire or a ground in the device removed.

Chart B-4, Grounded Serial Data Circuit. Scheme 45

CHART B-5, SERIAL DATA CIRCUIT OPEN

The serial data line, with the exception of the ECM, is redundant with all the devices that communicate with it. While only one line need be connected to each device for the system to function, when making repairs, both lines should be made to communicate. If the system shuts down when the ALDL cover is removed, a single open existed and a second open is being created by removing the ALCL cover.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks for serial data to the IPC. If less than one volt, re-establish serial data communications with the BCM before proceeding.
2. With serial voltage at the proper level, the fault is poor contact between the ECM and the IPC.

Chart B-5, Serial Data Circuit Open. Scheme 46

CHART B-6, SERIAL DATA SHORTED TO VOLTAGE

With a shorted serial data circuit, the BCM will not be able to communicate with the other devices in the system. Voltage measured anywhere along the circuit will be more than 5 volts. The only display on the IPC is "ELECTRICAL PROBLEM".

Note. Test number refers to number on diagnostic chart.

This step splits the system in half to help isolate the source of the short in the serial data line. If taking the ECM out of the system allows both halves of the serial data line to fall to less than 5 volts, the source of the short was in the module.

All subsequent steps follow the same pattern in that the components are removed from the serial data line until the normal voltage range is measured. When the section of the circuit is isolated, a simple check of the wire for a short to voltage differentiates between a shorted wire and a short in the device removed.

Chart B-6, Serial Data Shorted To Voltage. Scheme 47

CHART C-1, LOSS OF ECC COMMUNICATIONS

When the ECC communications are lost, "Service Diagnostics" usually cannot be entered, but a quick scan of the panel will usually isolate the source of the fault. The ECC panel is powered by the ignition. If the source of the power is lost, the ECC will usually display a segment check. Loss of serial data will result in 3 dashes (---) being shown on the panel VF display. This indicates power and ground are okay. If the panel displays normal outside or interior set temperature, power, ground and serial communications are being received, thus panel replacement is indicated.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks for voltage and ground to the panel. Test light should be on for both power to ground checks.
2. This step checks for serial data voltage. Normal voltage reading should be more than one volt and varying. A steady reading indicates a 2nd open exists or the ALDL cover is off. If a 2nd open is suspected, see CHART B-5.

Chart C-1, Loss Of ECC Communications. Scheme 48

CHART C-2, DIAGNOSTICS CANNOT BE ENTERED

When "Service Diagnostics" cannot be entered, a quick scan of the panel will help isolate the source of the fault. The ECC panel is powered by the ignition. If the source of power is lost, the ECC panel VF display will be blank. If the ground source is lost, a segment check will usually result. Loss of serial data will result in 3 dashes (---) being displayed, which indicates power and ground are okay. For these symptoms, see CHART C-1.

If the panel displays normal outside or interior set temperature, power and serial data communications are okay. Replacement of the ECC panel is necessary. When this is the case, the equivalent buttons for heating and A/C control will usually be inoperative.

1. If ECC does not display temperature or if a segment check is displayed, refer to CHART C-1.
2. If temperature is displayed and ECC buttons will not allow diagnostics to be entered, or if the ECC operation is erratic, replace ECC unit.

Chart C-2, Diagnostics Cannot Be Entered. Scheme 49

CHART C-2A, INJECTOR BALANCE TEST

Note. If it is determined that injectors are dirty, they should be cleaned using approved injector cleaning procedures prior to performing this test. Complete CHART A-7, FUEL SYSTEM DIAGNOSIS before starting this test.

The injector balance test is used to pulse the injector for a precise amount of time, spraying a measured amount of fuel in the intake manifold. As each injector is pulsed, a drop in fuel rail pressure occurs. This pressure drop can be recorded and compared to other injectors. An injector that has a pressure drop difference of 1.5 psi (.11 kg/cm 2 ) or more, greater or less than other injectors, should be considered faulty.

Note. Allow engine to cool down to avoid irregular readings due to "Hot Soak" fuel boiling. In order to prevent flooding, the INJECTOR BALANCE TEST should not be repeated more than once, without starting and running engine.

1. With ignition off, connect Fuel Pressure Gauge (J34730-1) to pressure tap. Unplug harness connector at all injectors. Connect Injector Tester (J 34730-3) to one of the injectors. On turbocharged engines, use adapter harness supplied with injector tester to pulse injectors that are not accessible.
2. Follow manufacturer's instructions for use of the adapter harness. Ignition should be turned off for at least 10 seconds to complete ECM shutdown cycle.
3. Turn ignition on. Fuel pump should run at least 2 seconds after ignition is turned on. Bleed air from gauge and hose to ensure accurate gauge reading. Repeat this procedure until all air is bled from system. Turn ignition off for at least 10 seconds.
4. Turn ignition on again to bring fuel pressure to maximum. Record initial pressure reading. Energize tester one time and note pressure drop at lowest point.
5. Disregard any slight pressure drop after low point is reached. Subtracting second pressure reading from initial reading indicates amount of injector pressure drop.
6. Repeat test step 4) on each injector and compare amount of pressure drop. Recheck injectors that do not read within pressure drop range. Replace injector(s) that fail second check.
7. If injectors are all okay, plug in harness connectors and review SYMPTOMS under TROUBLE SHOOTING in the article «FUEL INJECTION SYSTEM - MULTI-PORT»(/oldsmobile/toronado/iv-1985-1992/remont/testing-diagnostics/#fuel-injection-system-multi-port) in the ENGINE PERFORMANCE section.

Chart C-2A, Injector Balance Test. Scheme 50

CHART C-2C, IDLE AIR CONTROL (IAC) VALVE CHECK

The ECM controls idle RPM using the IAC valve. To increase idle RPM, the ECM retracts the IAC, allowing more air to pass around throttle plate. To decrease RPM, ECM extends IAC valve, reducing airflow around throttle plate. The "Scan" tester will read ECM commands to IAC valve in counts (0-255). The greater the counts, the more air allowed (higher idle). The less the counts, the less air allowed (lower idle).

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

1. Continue with test, even if engine will not idle. If idle is too low, data ED22 will display 80 or more counts, or steps. If idle is high, it will display zero counts. Occasionally an erratic or unstable idle may occur. If engine speed varies 200 RPM or more up and down, disconnect IAC. If the condition is unchanged, the IAC is not at fault.
2. When engine was stopped, IAC valve is retracted (more air) to a fixed "Park" position for increased airflow and idle speed during next engine start. Data ED22 will display 100 or more counts.
3. Ensure that IAC valve is unplugged prior to this test. Test light will confirm ECM signals by a steady or flashing light on all circuits.
4. There is a remote possibility that one of the circuits is shorted to voltage, which would have been indicated by a steady light. Unplug ECM and turn ignition on, and probe terminals to check for this condition.

Diagnostic Aids

A slow unstable idle may be caused by a system problem than cannot be overcome by the IAC. The data ED22 counts will be greater than 60 if too low, and zero counts if too high.

If idle is too high, stop engine. With ignition on, ground diagnostic terminal and wait 30 seconds for IAC to seat, and disconnect IAC. Unground diagnostic terminal and start engine. If idle speed is more than 750-850 RPM, locate and correct vacuum leak. For other causes of an improper idle, check the following

1. System too lean - Idle speed may be too high or too low, or engine running speed may vary up and down, and unplugging IAC does not help. A Code EO44 may have been set. The data ED07 will read an oxygen sensor output less than .3 volt. Check for low regulated fuel pressure or water in fuel. A lean exhaust, with an oxygen sensor output fixed greater than .8 volts indicates sensor contaminated with silicone.
2. System too rich - Idle speed too low. Data ED22 counts will be usually greater than 80. System is obviously rich and may exhibit Black exhaust smoke. The data ED07 will read an oxygen sensor signal fixed greater than .8 volt. Check for high fuel pressure or injector leaking or sticking.
3. Throttle body - Remove IAC and inspect for foreign material or evidence of IAC valve dragging the bore.

Chart C-2C, Idle Air Control (IAC) Valve Check. Scheme 51

CHART C-3, CANISTER PURGE CHECK

Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when energized. The ECM supplies a ground to energize the solenoid (purge on).

The purge solenoid is energized (purge on) if the diagnostic test terminal is grounded with the engine stopped or if following conditions are met

1. Engine run time is more than one minute.
2. Coolant temperature more than 176°F (80°C).
3. Vehicle speed more than 5 MPH
4. Throttle position sensor voltage greater than .75 volt.

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

1. Checks to see if solenoid is opened or closed. Solenoid is normally de-energized in this test, indicating it should be closed.
2. This test completes functional check by grounding test terminal. This should normally energize solenoid and allow vacuum to drop (purge on).
3. This test checks for open or shorted solenoid circuit. Solenoid coil resistance must measure greater than 20 ohms.

Chart C-3, Canister Purge Check. Scheme 52

CHART C-4F-1, C(3)I MISFIRE AT IDLE

The C(3)I ignition system uses a waste spark method of spark distribution. This type of ignition module triggers the No. 1 and 4 coil, resulting in both No. 1 and 4 spark plugs firing at the same time. No. 1 cylinder is on the compression stroke at the same time No. 4 is on the exhaust stroke, resulting in a lower energy requirement to fire No. 4 spark plug. This leaves the remaining high voltage to fire No. 1 spark plug.

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

1. If misfire problem exists under load only, see CHART C-4F-2. Engine RPM should drop equally on all plug leads.
2. Spark Tester (ST-125 ) must be used because it is essential to verify adequate available secondary voltage (25,000 volts) at spark plug.
3. By grounding opposite plug lead of the affected coil, a faulty spark plug (extremely high resistance) may be detected.
4. If ignition coils are carbon tracked, the coil tower spark plug wire nipples may be damaged.
5. By switching a normally operating coil into the position of the malfunctioning one, a determination can be made as to fault being the coil or ignition module.

Chart C-4F-1, C(3)I Misfire At Idle. Scheme 53

CHART C-4F-2, C(3)I MISFIRE UNDER LOAD

The C(3)I ignition system uses a waste spark method of spark distribution. On this type of ignition system the ignition module triggers the No. 1 and 4 coil, resulting in both No. 1 and 4 spark plugs firing at the same time. No. 1 cylinder is on the compression stroke at the same time No. 4 is on the exhaust stroke, resulting in a lower energy requirement to fire No. 4 spark plug. This leaves the remaining high voltage to fire No. 1 spark plug.

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

1. If the misfire problem exists at idle only, see CHART C-4F-1. Spark Tester (ST-125 ) must be used because it is essential to verify adequate available secondary voltage (25,000 volts) at the spark plugs. Spark should jump the tester gap on all 6 leads. This simulates a "load" condition.
2. By grounding the opposite plug lead of the affected coil, a faulty spark plug (extremely high resistance) may be detected.
3. If ignition coils are carbon tracked, the coil tower spark plug wire nipples may be damaged.
4. By switching a normal operating coil into the position of a malfunctioning one, a determination can be made if the coil or ignition module being at fault.

Chart C-4F-2, C(3)I Misfire Under Load. Scheme 54

CHART C-5, ELECTRONIC SPARK CONTROL (ESC) SYSTEM CHECK

The knock sensor is used to detect engine detonation and ECM will retard the electronic spark timing based on signal being received. The circuitry, within the knock sensor, causes ECM's supplied 5-volt signal to be pulled down so that under a no knock condition, circuit No. 496 would measure about 2.5 volts. The knock sensor produces an AC signal, which rides on the 2.5 volts (DC voltage). The amplitude and frequency are dependent upon the knock level.

The MEM-CAL used with this engine, contains functions which were part of remotely mounted ESC modules used on other GM vehicles. The ESC portion of the MEM-CAL, sends a signal to other parts of the ECM which adjusts spark timing to retard spark and reduce detonation.

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

1. With engine idling, there should not be a knock signal present at ECM, because detonation is not likely to occur under no load condition.
2. Tapping engine lift hook should simulate a knock signal to determine if sensor is capable of detecting detonation. If no knock is detected, try tapping on engine block closer to sensor before replacing sensor.
3. If engine has an internal problem which is creating a knock, knock sensor may be responding to internal failure.
4. This test determines if knock sensor is faulty or if ESC portion of MEM-CAL is faulty. If it is determined that MEM-CAL is faulty, ensure that it is properly installed and latched into place. If not properly installed, repair and retest.

While observing knock signal on data ED17, there should be an indication that knock is present, when detonation is audible. Detonation is most likely to occur under high engine load conditions.

Chart C-5, Electronic Spark Control System Check. Scheme 55

CHART C-7, EXHAUST GAS RECIRCULATION (EGR) FLOW CHECK

The digital (EGR) valve is designed to accurately supply EGR to an engine independent of intake manifold vacuum. The valve controls EGR flow from the exhaust to the intake manifold through 3 orifices which increment in size to produce 7 combinations. When a solenoid is energized, the armature, with attached shaft and swivel pintle, is lifted opening the orifice. The flow accuracy is dependent on metering orifice size only, which results in improved control.

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

If a code is set, inspect EGR for damage. Start and idle engine, enter ECM overrides data ES02, ES03 and ES04. You should be able to discern a change in engine RPM as the ECM turns on the EGR. Data ES02 should result in a small change and data ES04 in a large change in RPM. The engine may stall when data ES04 is turned on.

Chart C-7, Exhaust Gas Recirculation Flow Check. Scheme 56

CHART C-8A, TORQUE CONVERTER CLUTCH (TCC)

The purpose of the torque converter clutch is to eliminate the power loss of the torque converter when vehicle is in cruise condition. This allows the convenience of automatic transmission and fuel economy of a manual transaxle. The heart of the system is a solenoid located inside the transaxle which is controlled by the ECM.

When solenoid coil is activated (on), the torque converter clutch is applied which results in straight through mechanical coupling from engine to drive wheels. When the transaxle (TCC) solenoid is deactivated, the torque converter clutch is released which allows the torque converter to operate in the conventional manner (fluidic coupling between engine and transaxle).

TCC will engage under given road load in 3rd and 4th gear.

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

1. "LO" display confirms that 4th gear switch is closed.
2. At 45 MPH the transaxle 4th gear switch should open resulting in IPC displaying "HI".
3. Entering ECM diagnostics output data EO01 should cause the solenoid to cycle on and off at 3 second intervals. This test checks the capability of the ECM to control the solenoid driver circuit.
4. Solenoids are turned on or off by the ECM internal electronic switches called "drivers". Each driver is part of a group of 4, called Quad-Drivers. Using an ohmmeter, check the solenoid coil resistance of the TCC. Coil resistance must measure greater than 20 ohms.

Chart C-8A, Torque Converter Clutch (TCC). Scheme 57

CHART C-12A, COOLANT FAN CHECK

On standard cooling applications, one fan, one low speed relay and one high speed relay are used. On V08 (heavy duty cooling) systems, the 2 coolant fans are energized through one low speed and 2 high speed relays.

Power for the fan is supplied through the fusible link to terminal No. 1 on all relays. The relays are energized when ECM (quad- drivers) ground circuit.

1. Low speed relay - The ECM energizes the relay through terminal "YC2" when coolant temperature reaches 208°F (101°C).
2. High speed relay - The high speed relay is energized by the ECM or the A/C pressure switch. If the A/C refrigerant pressure reaches 275 psi (19.3 kg/cm 2 ), or the coolant temperature reaches 226°F (108°C), the high speed fan relay will be energized.
3. Pusher fan relay - The pusher fan is installed as part of the heavy duty cooling package (V08) and is turned on anytime the high speed fan is running.

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

1. Codes EO14 or EO15 could indicate coolant system or sensor operation is not normal, so fan operation cannot be checked correctly.
2. ECM output EO09 grounds "LO" speed relay through the ECM for 3 seconds on, and 3 seconds off. "LO" speed fan should be on for 3 seconds and off for 3 seconds.
3. Grounding A/C pressure switch harness terminal "B" should energize high speed relay and fan should operate at high speed.

Chart C-12A, Coolant Fan Check. Scheme 58

CHART C-12B, COOLANT FAN CHECK

On standard cooling applications, one fan, one low speed relay and one high speed relay are used. On V08 (heavy duty cooling) systems, the 2 coolant fans are energized through one low speed and 2 high speed relays.

Power for the fan is supplied through the fusible link to terminal No. 1 on all relays. The relays are energized when ECM (quad drivers) ground circuit.

1. Low speed relay - The ECM energizes the relay through terminal "YC2" when coolant temperature reaches 208°F (101°C).
2. High speed relay - The high speed relay is energized by the ECM or the A/C pressure switch. If the A/C refrigerant pressure reaches 275 psi (19.3 kg/cm 2 ), or the coolant temperature reaches 226°F (108°C), the high speed fan relay will be energized.
3. Pusher fan relay - The pusher fan is installed as part of the heavy duty cooling package (V08) and is turned on anytime the high speed fan is running.

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

1. Test light should be on, as harness terminal No. 2 has battery voltage with ignition switch in "ON" position.
2. Test light should be on for 3 seconds and off for 3 seconds, as EO09 cycles fan on/off at 3 second intervals.
3. Jumpering harness terminals No. "1" and "4" by-passes relay. If fan runs, relay is faulty.
4. If circuit No. 2 was open, test light would not illuminate.
5. Cycling of the test light verifies circuit No. 532 and 150 are okay, indicating fan motor is faulty.

Chart C-12B, Coolant Fan Check. Scheme 59

CHART C-12C, COOLANT FAN CHECK

On standard cooling applications, one fan, one low speed relay and one high speed relay are used. On V08 (heavy duty cooling) systems, the 2 coolant fans are energized through one low speed and 2 high speed relays.

Power for the fan is supplied through the fusible link to terminal No. 1 on all relays. The relays are energized when ECM (quad- drivers) ground circuit.

1. Low speed relay - The ECM energizes the relay through terminal "YC2" when coolant temperature reaches 208°F (101°C).
2. High speed relay - The high speed relay is energized by the ECM or the A/C pressure switch. If the A/C refrigerant pressure reaches 275 psi (19.3 kg/cm 2 ), or the coolant temperature reaches 226°F (108°C), the high speed fan relay will be energized.
3. Pusher fan relay - The pusher fan is installed as part of the heavy duty cooling package (V08) and is turned on anytime the high speed fan is running.

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

1. Test light should be on, as harness terminal No. 2 has battery voltage with ignition switch in "ON" position.
2. Test light should be on for 3 seconds and off for 3 seconds, as EO10 cycles fan on/off at 3 second intervals.
3. Jumpering harness terminals No. "1" and "4" by-passes relay. If fan runs, relay is faulty.
4. If circuit No. 2 was open, test light would not illuminate.
5. Cycling of the test light verifies circuit No. 533 and 150 are okay, indicating fan motor is faulty.

Chart C-12C, Coolant Fan Check. Scheme 60

CHART C-12D, COOLANT FAN CHECK

On standard cooling applications, one fan, one low speed relay and one high speed relay are used. On V08 (heavy duty cooling) systems, the 2 coolant fans are energized through one low speed and 2 high speed relays.

Power for the fan is supplied through the fusible link to terminal No. 1 on all relays. The relays are energized when ECM (quad-drivers) ground circuit.

1. Low speed relay - The ECM energizes the relay through terminal "YC2" when coolant temperature reaches 208°F (101°C).
2. High speed relay - The high speed relay is energized by the ECM or the A/C pressure switch. If the A/C refrigerant pressure reaches 275 psi (19.3 kg/cm 2 ), or the coolant temperature reaches 226°F (108°C), the high speed fan relay will be energized.
3. Pusher fan relay - The pusher fan is installed as part of the heavy duty cooling package (V08) and is turned on anytime the high speed fan is running.

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

1. Checks to see if circuit No. 535 is shorted to ground, which would cause the low speed relay to be energized at all times.
2. If relay is faulty, test light will not illuminate. If test light is illuminated, temperature, A/C high pressure or circuit No. 536 is shorted to ground.
3. If test light is off, the relay is faulty. If test light is on, the A/C high pressure fan switch, ECM or circuit No. 535 is shorted to ground.

Chart C-12D, Coolant Fan Check. Scheme 61

PFI Components 3.8L 3800 ECM/BCM Engine (VIN C). Scheme 62

ECM TERMINAL ID

This ECM voltage charts can be used with a digital voltmeter to help save time in diagnosis. Voltages on the car being tested may vary slightly from these due to battery voltage or alternator charging level.

The following conditions must be met before testing

1. Engine at operating temperature.
2. Engine in closed loop operation.
3. Engine idling ("Engine Run" column).
4. Test terminal NOT grounded.
5. Scanner or ALDL tool NOT installed.

PFI ECM Pin ID 3.8L 3800 ECM/BCM Engine (VIN C) (1 of 3). Scheme 63

PFI ECM Pin ID 3.8L 3800 ECM/BCM Engine (VIN C) (2 of 3). Scheme 64

PFI ECM Pin ID 3.8L 3800 ECM/BCM Engine (VIN C) (3 of 3). Scheme 65

BCM Circuit Schematic (Part 1 of 4). Scheme 66

BCM Circuit Schematic (Part 2 of 4). Scheme 67

BCM Circuit Schematic (Part 3 of 4). Scheme 68

BCM Circuit Schematic (Part 4 of 4). Scheme 69

Circuit Schematic (Part 1 of 4). Scheme 70

Circuit Schematic (Part 2 of 4). Scheme 71

Circuit Schematic (Part 3 of 4). Scheme 72

Circuit Schematic (Part 4 of 4). Scheme 73

BCM Wiring Diagram. Scheme 74

See also:
• FUEL INJECTION SYSTEM - MULTI-PORT