3.8l BCM Tests W/codes Buick Riviera VII

DESCRIPTION

Note. For information on Engine Control Module (ECM) controlled systems, see 3.8L (3800 VIN [C]) ECM TESTS W/CODES.

Reatta, Riviera and Toronado models use several electronic components which can be controlled by the service technician to provide valuable self-diagnostic information. The components are part of an electrical network designed to control various engine and body subsystems. This article will provide a description of the overall electronic network and the on-board diagnostic capabilities which have been designed to aid the service technician in system diagnosing and testing.

At the heart of the computer system is the Body Control Module (BCM). The BCM is located behind the instrument panel, above fuse block (behind upper right side of instrument panel, on Reatta and Riviera models). The BCM has an integral microprocessor, which is the center for communication with all other components in the system. All sensors and switches are monitored by the BCM or one of the other major components that complete the computer system. The other major components are: Electronic Control Module (ECM), Instrument Panel Cluster (IPC), Cathode Ray Tube Controller (CRTC) (optional on Toronado), Electronic Heater and A/C Control (ECC) (Toronado), Programmer-Heating and A/C (HVAC), and an optional compass (Reatta and Riviera).

COMPONENT LOCATIONS

Note. For component location and identification during testing (Scheme 1)

Scheme 1

OPERATION

A combination of inputs from the major components, sensors and switches, communicate together with the BCM. Various inputs to the BCM combine with program instructions within system memory, providing accurate control over all subsystems involved. When a subsystem circuit exceeds preprogrammed limits, a system malfunction is indicated and certain back-up functions maybe provided. The BCM controls subsystems through direct outputs or through data transmitted along the serial data line to one of the other major components. The process of receiving', storing; testing and control- ling information is continuous. The data communication gives the BCM control over the ECM's self-diagnostic capabilities in addition to its own. Between the BCM and the other 4 major components of the computer system, a communication process has been incorpo- rated, that allows devices to share information and thereby provide for additional control capability.

CATHODE RAY TUBE CONTROLLER

In order to access and control the BCM self-diagnostic features, 2 additional electronic components are used. The 2 components are the Cathode Ray Tube Controller (CRTC) and Cathode Ray Tube (CRT) picture tube. The CRT's "SERVICE MODE" incorporates a 22-character display area, which is used to display diagnostic information. When a malfunction is sensed by the computer system, one of the driver warning messages is displayed on the CRT under the "DIAGNOSTIC" category. When the "SERVICE MODE" is entered, various BCM, ECM or IPC faults can be displayed. In addition to the parameters, fault codes, inputs and outputs, are other features such as override commands, snapshot, display VIN and code clearing capability. This information can be accessed and displayed when commanded through the CRT. The CRT becomes the device in which to enter diagnostics and access service diagnostic routines. The CRTC is the device which controls display and interprets switches touched on the CRT. CRTC passes this information to the BCM. This communication process allows the BCM to transfer any of its available diagnostic information to the CRT for display during "SERVICE MODE". By touching the appropriate pads on the CRT, data messages can be sent to the BCM from CRTC over the data line, requesting specific diagnostic features. Below is a list of computer controlled subsystems.

1. Climate Control
2. Instrument Panel Displays
3. Illuminated Entry
4. CRT Display
5. Chime
6. Dimming (Lighting)
7. Twilight Sentinel
8. Cruise Control
9. Courtesy Lights
10. Compass
11. Generator Control System
12. Self-Diagnostics System
13. ECM Subsystems
14. Radio
15. Gauges
16. Trip Data
17. Driver Diagnostics
18. Phone

ELECTRONIC CLIMATE CONTROL (ECC) (TORONADO)

The ECC panel provides the controls, for heating and A/C systems. It also becomes the controller by which to enter diagnostics and access BCM self-diagnostics. This communication process allows BCM to transfer any of its available diagnostic information to the instrument panel for display during service. By pressing the appropriate buttons on the ECC, data messages can be sent to the BCM over the serial data line, requesting specific diagnostic features. When in the override mode of BCM diagnostics, the amount of override is displayed at the ECC, where outside and set temperature are normally displayed.

Trouble Codes

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

An alpha-numeric 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.

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.

Reatta & Riviera

Turn ignition on. Touch "OFF" and "WARM" key pads on. CRT climate control page simultaneously and hold until a double "Beep" is heard or a page entitled "SERVICE MODE" appears on the screen. (Scheme 2)

Toronado (CRT)

Turn ignition on. Touch "OFF" and "WARM" buttons on secondary display simultaneously and hold until segment check is displayed on the Instrument Panel Cluster (IPC). On vehicles equipped with a color CRT, the "OFF" hardkey and "WARM" softkey should be used. (Scheme 2)

Toronado (ECC Panel)

Turn ignition on. 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 3)

When in the "SERVICE MODE", the climate control will continue to operate in the setting prior to entering "SERVICE MODE". Also, during "SERVICE MODE" operation, the climate control can be operated the same as normal, by touching climate control border key pad and calling up climate control page.

To re-enter "SERVICE MODE" page, touch the border key pad marked status. The climate control and status border key pads are the only 2 border key pads that will operate in "SERVICE MODE".

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

Toronado

When in the "SERVICE MODE", the climate control will continue to operate in whatever setting it was in prior to "SERVICE MODE". Even though display may change as buttons are touched, the previous operating mode is stored 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.

Upon completion of trouble code display, a specific system may be selected for testing. Following the trouble code display, the first available system will be displayed (i.e.- ECM). When making system selections there are 3 available alternatives.

1. Pressing the "LEVEL" pad will stop system selection process and return system to beginning of trouble code sequence.
2. Pressing the "NO" key pad will display the 'next available system selection. This allows display to be stepped through all system choices. This list of systems can be repeated following display of the last system.
3. Pressing the "YES" key pad will select the displayed system for testing. At this point the first available test type will appear with selected system name above.

Upon completion of trouble code display, a specific system may be selected for testing. Following the trouble code display, the first available system will be displayed (i.e. ECM). When making system selections there are 4 available alternatives.

1. Pressing the "LEVL" pad will stop system selection process and return system to beginning of trouble code sequence.
2. Pressing the "NO" key pad will display the next available system selection. This allows display to be stepped through all system choices. This list of systems can be repeated following display of last system.
3. Pressing the "YES" key pad will select the displayed system for testing.
4. Pressing the "RTN" key pad on' the secondary display will exit diagnostics and return to normal IPC, and secondary display operation.

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

Scheme 2

Scheme 3

Having selected a system, the first available test type will be displayed (i.e. "ECM DATA"). When making the selection of test type, the following are available test type alternatives.

1. Pressing the "LEVEL" key pad will stop test type selection and return display to next available system selection.
2. Pressing the "NO" key pad will display the next available test type for the selected system. This allows the display to be stepped through all available test type choices. This list of systems can be repeated following the end of system list.
3. Pressing the "YES" key pad will select the displayed test type. At this point, the display will either indicate that the selected test type is in progress or the first of several specific tests will appear. If "NO DEVICES" appears, no test is available.

Having selected a system, the first available test type will be displayed (i.e. "ECM DATA"). When making the selection of test type, the following are available test type alternatives.

1. Pressing the "LEVEL" key pad will stop test type selection and return display to next available system selection.
2. Pressing the "NO" key pad will display the next available test type for the selected system. This allows the display to be stepped through all available test type choices. This list of systems can be repeated following the end of system list.
3. Pressing the "YES" key pad will select the displayed test type. At this point the display will either indicate that selected test type is in progress or the first of several specific tests will appear.
4. Pressing the "RTN" key pad will exit diagnostics.

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 next available selection.
2. Pressing the "LOW" fan button will display the next available test type for 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, display will either indicate whether selected test type is in progress, or the first of several tests will appear.
4. Pressing the "BI-LEVEL" button will exit diagnostics.

Reatta, Riviera & Toronado (CRT)

Selection of "DATA", "INPUTS", "OUTPUTS", or "OVERRIDE" test types will result in the first available test being displayed. If dashes appear, this test is not permitted with the engine running. Turn engine off and begin again.

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

1. Pressing the "LEVEL" key pad will stop test selection process and return display to next test type for selected system.
2. Pressing the "NO" key pad will display the next smaller test number for selected test type. If this pad is pressed with lowest test number displayed, highest test number will appear.
3. Pressing the "YES" key pad will display the next larger test number for selected test type. If this key pad is touched with highest test number displayed, lowest test number will appear.

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

Pressing the "SLEW L" and "SLEW O" key pad on secondary display panel starts override, at which time the display will no longer alternate to "----". Pressing "SLEW L" key pad increases value, while "SLEW O" key pad decreases value. Normal program control can be resumed in one of 3 ways

1. Selection of another override will cancel current override.
2. Selection of another system (ECM, BCM or IPC) will cancel current override.
3. Overriding value beyond either extreme (0-99) will display "----" momentarily and then jump to extreme opposite. If key pad is released while "----" is displayed, normal program control will resume and display will again alternate.

Scheme 4

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

The last 4 characters of display will contain a test code to identify selection. The first 2 of these characters are letters which identify the system and 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 test, the following actions may be taken to control display

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

Scheme 5

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

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

1. Selection of another override test will cancel current override.
2. Selection of another system (ECM, BCM or IPC) will cancel current override.
3. Overriding the value beyond either extreme (0 or 99) will display "--" momentarily and then jump to opposite extreme. If button is released while "--" is being displayed, normal program control will resume and 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 secondary display 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 override on different vehicle parameters.

Selection of "CODE RESET" test type, will result in the message "CODES CLEAR" being displayed with selected system name above, after "YES" pad has been touched. This message appears for 3 seconds indicating that all stored trouble codes have been erased from memory. After this 3-second message, display will automatically return to next available test type for s selected system.

Toronado (ECC Panel & CRT)

Selection of "CLEAR CODES" test type will result in the message "CODES CLEAR" being displayed along with the selected system name. This message will appear for 3 seconds to indicate that all stored trouble codes have been erased from that system's memory. After 3 seconds, the display will automatically return to the next available test type for the selected system.

Scheme 6

Reatta & Riviera (BCM Snapshot)

Selection of "SNAPSHOT?" test type will result in the message "SNAPSHOT TAKEN", being displayed with selected system name preceding it, for the ECM. The BCM will result in the message "BXXX Snapshot" being displayed. The "B" stands for BCM and the following 3 numbers indicate the diagnostic code that triggered snapshot, or selecting manual trigger event. While selecting a specific event, any of the following actions may be taken to continue display.

The "LEVEL" pad can be pressed to return to next level in the same system (the BCM will hold 3 snapshots for codes based on the 3 most recent codes). The "NO" pad will cause display of the next code that triggered a snapshot; or, if there are no other codes, will display the message for a manually triggered snapshot, "TAKE BCM SNAPSHOT?". This message will also be displayed after the 3rd (and last) snapshot held in BCM memory.

Pressing the "YES" pad will cause display to proceed to first available snapshot test type, if code is triggered, or if display reads "SNAPSHOT TAKEN" message for 3 seconds and automatically proceeds to first available snapshot test type, if manually triggered.

From this point "Snapshot Test Type" for both ECM and BCM systems operate the same. The only difference is that ECM has only a manual trigger for snapshot, while BCM has manual trigger and memory for storing snapshot information on last 3 codes set.

The "SNAPSHOT TAKEN" message, on manually triggered snapshots, will appear for 3 seconds, indicating that all system data and inputs have been stored in memory. After 3 seconds display will automatically proceed to first available snapshot test type (e.g. SNAP DATA). While selecting a snapshot test type, any of the following actions may be taken to control display

1. Pressing the "LEVEL" button on CRT will stop test type selection process and return display to next available system selection, or event.
2. Pressing the "NO" button will display next available snapshot test type. This allows display to be stepped through all available choices. The list of snapshot test types can be repeated following display of last choice.
3. Pressing the "YES" button with "SNAP DATA?"/"BXXX DATA?" or "SNAP INPUTS"/"BXXX INPUTS?" displayed will select that test type. Display is now controlled as it would be for non-snapshot data and inputs displays. However, all values and status information represents memorized vehicle conditions.
4. Pressing the "YES" button with "SNAPSHOT?" displayed will again display "SNAPSHOT TAKEN" message, indicating that new information has been stored in memory. Access to this information is obtained the same as previously described.

Toronado BCM Snapshot (ECC Panel)

Selection of "SNAPSHOT?" test type while in BCM system level will allow recall of up to 3 snapshots recorded at the time of setting BCM malfunction codes. It is possible to trigger the recording of a snapshot upon demand. Selecting snapshot (pushing the "HI" button) while in BCM system, will result in 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 display

1. Pressing the "OFF" button on ECC panel will end test type selection process and return display to next available system selection.
2. Pressing the "LO" button will allow scrolling through stored BCM diagnostic codes, possessing a snapshot. After the last diagnostic code, (or the third if there are more than 3 codes set) pressing "LO" button will result in "TAKE BCM SNAPSHOT?" display. Responding "LO" will return to first "BXXX SNAP?" display.
3. Pressing the "HI" button with "SNAP DATA?" or "SNAP INPUTS?" displayed, will select that test type. 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 "SNAP DATA?" displayed will again display "SNAPSHOT TAKEN" message indicating that new information has been stored in memory. Access to this information is obtained the same as previously described

When ignition is turned on and vehicle is in Park, pressing "TEST" button on IPC will cause IPC to sequentially illuminate and darken all segments and telltales in cluster. This helps in determining if any bulbs or segments of instrument cluster vacuum fluorescent display are out, or always on. In order to give technician more time to study the various segments (whenever in the "SERVICE MODE" and not running a test) pressing "TEST" button will run segment check 10 times slower.

When ignition is turned on and "SYSTEM MONITOR" button is pressed, the BCM will cause the IPC 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. This also allows 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 will also occur.

To exit the service mode, repeatedly press the "LEVEL" pad until "SERVICE MODE" page disappears or press "END" pad, or turn ignition off. Trouble codes are not erased when this is done.

To exit diagnostics, depress "RTN" button on CRT or turn ignition off. Trouble codes are not erased when this is done.

To exit diagnostics, depress "BI-LEVEL" button on ECC or turn ignition off. Trouble codes are not erased when this is done.

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 switched inputs are properly interpreted. When one of the input tests is selected, the state of that device is displayed as "HI" or "LO". Basically, "HI" or "LO" represent input terminal voltage for that circuit.

Also, the display indicates if input changed state since 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 indicating 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. On Reatta and Riviera models, upon selecting a test, that selection's current operation will be represented as a percentage of its full range. This value will be displayed on the CRT below the "EXIT" key pad.

Pressing key pads above or below "OVERRIDE" ("WARM" or "COOL" on Toronado) on the CRT begins the override. When in override, pressing key pad above "OVERRIDE" increases the value, while pressing key pad below decreases the value. Normal program control can be achieved in 3 ways.

1. Selection of another override test will cancel the current override.
2. Selection of another system will cancel the current override.
3. Overriding the value beyond either extreme (0 or 99) will display "---" momentarily and then jump to the normal program control.

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. After selection of an override test, pressing the "LEVEL" ("OFF" on Toronado) key pad will allow selection of another test type, yet the CRT will continue to display the selected override. When selecting another test or type, and then pressing the key pads above or below "OVERRIDE" ("WARM" or "COOL" on Toronado), it is possible to monitor the effect of override on different vehicle parameters.

BCM OVERRIDE DISPLAY CODES

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

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

After diagnostics is entered, any trouble codes stored in computer will be displayed. ECM codes will be displayed first. If no ECM codes are stored, display will indicate "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 primarily 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 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 "LO" fan button is pressed anytime during display of ECM and BCM codes, display of codes will be by-passed. If at any time "BI-LEVEL" button is pressed, BCM will exit "SERVICE MODE" and return to normal vehicle operation.

BCM TROUBLE CODES

PRELIMINARY PROCEDURES

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

1. Check to see if "SERVICE ENGINE SOON" light is working. If this light fails to illuminate 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 his case, the "SELF-DIAGNOSTIC SYSTEM CHECK" will direct you to the appropriate diagnostic chart.
3. Are there any trouble 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.

HOW TO USE THIS SECTION

This portion of article is used only AFTER you have checked the following

1. Verify the on-car diagnostics are working by performing appropriate DIAGNOSTIC CIRCUIT CHECK chart for that system.
2. Verify that the ECM and "SERVICE ENGINE SOON" light are functioning properly.
3. Verify that there are no trouble codes stored, or only intermittent ones.
4. Perform FUEL SYSTEM PRESSURE TEST.
5. Perform a careful visual inspection of all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. Not all items listed under each symptom apply to all models and systems. These procedures will normally lead you to a component system on vehicle, such as EGR, EST, TCC, etc. These are covered in component system charts. These charts are listed with a "C" before the number of the chart (C-1A, for example).

FUEL SYSTEM PRESSURE TEST

Note. Trouble shooting and diagnosis of fuel system should begin with determining fuel injection system pressure. Before replacing fuel system components, fuel pressure must be relieved from system.

1. Connect Fuel Pressure Gauge (J-34730-1) to fuel pressure connector in fuel rail. To reduce possibility of fuel spillage and possible fire hazard, wrap shop cloth around fitting while connecting or disconnecting gauge.
2. To bleed pressure from system for component replacement, insert bleed hose into an appropriate container and open gauge valve.
3. With gauge installed at fuel rail connector, turn ignition on. With ignition on and engine off, pressure should read 40-47 psi (2.8-3.3 kg/cm 2 ). Start engine. Pressure should drop 3-10 psi (.2-7 kg/cm 2 ). For further details on fuel system pressure testing, proceed to appropriate CHART A-7 for that system.

Symptom Definition

"SERVICE ENGINE SOON" light comes on but does not stay on. A stored code may or may not exist.

Possible Cause & Correction

To track down possible causes of an intermittent "SERVICE ENGINE SOON" light check the following items.

1. Check for poor mating of one connector to another. Terminals may not be fully seated. Check for improperly formed or damaged terminals. Check wire to terminal connections.
2. Check for poor connection from coil pack to ground or arcing at spark plug wires or plugs.
3. Check wire from "SERVICE ENGINE SOON" light to ECM for short to ground.
4. Check wire from ALDL terminal "D" for intermittent short to ground.
5. Check for poor connections in ECM ground terminals.
6. Check for loss of trouble code memory. To check code memory, disconnect TPS and run engine at idle until "SERVICE ENGINE SOON" light comes on. Code EO22 should be stored and retained in memory when ignition is turned off. If not, ECM is faulty.
7. Check for electrical system interference caused by a defective relay or an ECM driven solenoid or switch which may cause a sharp electrical surge. This type of problem will normally occur when faulty component is operated.
8. Check for aftermarket parts which may not have been produced to manufacturers' specifications. Solenoids without original-equipment diodes for circuit protection or voltage regulator using transistors instead of silicone-chip circuitry may possibly cause voltage surges (up to 300 volts) in ECM wiring, causing temporary ECM shutdown. ECM shutdown is a normal response to system overvoltage (over 16 volts on most models). ECM will repower when condition ceases to exist. This could cause a flickering "SERVICE ENGINE SOON" light with no codes set in memory.
9. Check for improper installation of electrical accessories such as auxiliary lights or 2-way radios.

Engine cranks okay, but does not start for a long time. Engine eventually starts, may immediately die or run okay.

Check the following items.

1. Check fuel pump relay. To do this, connect test light between fuel pump test terminal and ground. Turn ignition on. Light should illuminate for 2 seconds. If not, see appropriate CHART A-5 FUEL PUMP RELAY CIRCUIT for that system.
2. Check for poor quality or water contaminated fuel.
3. Check that TPS is not sticking or binding.
4. Check EGR operation. See appropriate component CHART C-7 for that system.
5. Check for a leaking injector.
6. Check that resistance of coolant sensor circuit or coolant sensor is not too high. See CODE EO15 chart.
7. Check ignition system for bare or shorted wires. Check for adequate spark using Spark Tester (ST-125).
8. Check for shorts by spraying plug wires with a fine mist of water.
9. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
10. Check for correct fuel pressure in all speed ranges. See appropriate CHART A-7 for that system.
11. A faulty in-tank fuel pump check valve will allow fuel in lines to drain back to tank after engine is stopped. To check this condition, turn ignition off, disconnect fuel pressure line at fuel rail, remove filler cap, and connect a radiator test pump and apply 15 psi (1.0 kg/cm 2 ) pressure. If pressure will hold for 60 seconds, check valve is okay.
12. Check that PROM in vehicle is correct for that vehicle. Check with dealer for latest application information.
13. Check for restricted exhaust system.

Engine starts okay but dies after brief idle, dies as soon as any load is placed on engine (such as turning on air conditioner or engaging transmission), or on initial driveaway.

Check the following items.

1. Check for proper operation of Idle Air Control (IAC) system. See appropriate component CHART C-2 for that system.
2. Check PCV valve for proper operation.
3. Unplug MAF sensor. ECM will substitute a default value for MAF signal. If stall condition is eliminated, replace MAF sensor.
4. Check EGR system for proper operation. See appropriate component CHART C-7 for that system.
5. If stall occurs when air conditioner is turned on, check for air conditioner clutch signal to ECM terminal. Voltage at A/C terminal of ECM should be battery voltage when air conditioner compressor clutch is engaged. A high voltage surge due to a shorted compressor clutch diode could cause ECM shutdown.
6. Check for an overcharged air conditioner system.
7. Check for plugged or restricted fuel lines. See appropriate component CHART A-7, FUEL SYSTEM DIAGNOSIS for that system.
8. Using Spark Tester (ST-125), check for a weak spark.

Momentary lack of response when accelerator is pushed down. Can occur at all vehicle speeds. Usually occurs when taking off from a stop.

Check the following items.

1. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at coil pack and spark plugs.
2. Check wires for pinches, cuts, and proper connections.
3. Check that fuel pressure is correct in all speed ranges. See appropriate CHART A-7, FUEL SYSTEM DIAGNOSIS for that system. Also check for poor quality or water contaminated fuel.
4. Check for fouled spark plugs.
5. Check that PROM in vehicle is correct for that vehicle. Check with dealer for latest application information.
6. Check for a binding or sticking TPS.
7. Ensure that ECM controlled idle speed is correct.
8. Check EGR system for proper operation. See appropriate component CHART C-7 for that system.
9. Disconnect fuel injector electrical connectors. Crank engine and check for injector leaks.
10. Check canister purge system for proper operation.
11. Check charging system output. Repair charging system if voltage is less than 9 volts or greater than 16 volts.
12. Perform injector balance test.

Engine power varies under steady throttle or cruise. Feels like vehicle speeds up and slows down without changing position of accelerator pedal.

Check the following items.

1. Perform DIAGNOSTIC CIRCUIT CHECK.
2. Check that Park/Neutral switch is properly adjusted. See appropriate component CHART C-1A.
3. Check for intermittent open or short to ground in Torque Converter Clutch (TCC) circuit. See appropriate component CHART C-8 TORQUE CONVERTER CLUTCH for that system.
4. Check for proper operation of canister purge system. See appropriate component CHART C-3 for that system.
5. Check for proper operation of ESC system. See appropriate component CHART C-5 for that system.
6. Check for proper operation of EGR system. See appropriate component CHART C-7 for that system.
7. Check for adequate spark output using Spark Tester (ST-125).
8. Check O2 sensor for lead or RTV sealant contamination. This will cause a false high voltage signal to ECM. ECM will respond by leaning air/fuel ratio.
9. Check in-line fuel filter and replace if dirty or clogged.
10. Check fuel for water contamination. Check that fuel system pressure is correct at all engine speeds. See appropriate CHART A-7 FUEL SYSTEM DIAGNOSIS for that system.
11. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Also check condition of distributor cap, rotor and spark plug wires.
12. Check A/C for excessive charge.
13. Check for restricted exhaust system.

Engine delivers less power than expected. Little or no increase in speed when accelerator is depressed.

Check the following items.

1. Perform DIAGNOSTIC CIRCUIT CHECK for that system.
2. Check that air filter and fuel filter are not plugged. Replace if necessary. Check for incorrect fuel pressure. See appropriate component CHART A-7 for that system.
3. Check for proper operation of TCC system. See appropriate component CHART C-8 for that system.
4. Check ESC system for excessive retard. See appropriate component CHART C-5 for that system.
5. Ensure that EGR valve is not open all the time. See appropriate component CHART C-7 for that system.
6. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See appropriate CHART B-1, RESTRICTED EXHAUST SYSTEM CHECK for that system.
7. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
8. Using Spark Tester (ST-125), check for proper spark.
9. Check engine valve timing and compression.
10. Check engine for a worn camshaft.

Fuel ignites in intake manifold or in exhaust system creating a loud popping noise.

Check the following items.

1. Check for proper valve timing.
2. Check engine for sticking or leaking valves.
3. Using Spark Tester (ST-125), check available output voltage.
4. Check for crossfire between spark plugs and spark plug wires.
5. Check for an intermittent ignition system problem.

Engine runs unevenly at idle. If bad enough vehicle will shake. Idle may vary in RPM. Engine idles at incorrect RPM.

Check the following items.

1. Perform DIAGNOSTIC CIRCUIT CHECK.
2. Ensure that throttle linkage and/or TPS are not sticking or binding.
3. Check engine idle speed, both base idle and ECM idle.
4. Check Idle Air Control (IAC) system. Check for foreign material in IAC bore. See DIAGNOSTIC AIDS in appropriate component CHART C-2 for that system.
5. Check for proper operation of EGR system. See appropriate component CHART C-7 for that system.
6. Check P/N switch circuit. Also make sure that P/N switch is properly adjusted. See appropriate component CHART C-1 for that system.
7. Check power steering pressure switch circuit. See appropriate component CHART C-1 for that system.
8. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See appropriate CHART B-1, RESTRICTED EXHAUST SYSTEM CHECK for that system.
9. If rough idle only occurs when engine is hot, check PCV valve for proper operation, check evaporative emission control system, check for proper spark plug gap and check engine compression.

Engine starts but will not run at idle. Engine will run if accelerator is held at part throttle.

Check the following items.

1. Problem is most likely in Idle Air Control (IAC) system. See DIAGNOSTIC AIDS in appropriate code chart for that system.
2. Check EGR system. See appropriate component CHART C-7 for that system.
3. Check P/N switch. See appropriate component CHART C-1A for that system.
4. Disconnect MAF sensor. If condition is corrected, replace sensor.

Fuel economy, as measured by an actual road test, is noticeably lower than expected. Fuel economy is noticeably lower than was on this vehicle at one time.

Check the following items.

1. Check for a clogged air filter.
2. Check cooling system thermostat for proper heat range and operation.
3. Check coolant sensor for shift in calibration. Use temperature-to-resistance chart in Code EO14 or EO15 chart.
4. Ensure that speedometer is properly calibrated.
5. Check engine compression.
6. Check for dragging brakes.
7. Check A/C for "full time" operation.
8. Check for proper EST and ESC operation. See appropriate component CHART C-4 and C-5 for that system.
9. Check for proper operation of Torque Converter Clutch (TCC). See appropriate component CHART C-8 for that system.
10. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See appropriate CHART B-1, RESTRICTED EXHAUST SYSTEM CHECK for that system.
11. Check oxygen sensor for silicone or lead contamination.
12. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
13. Ensure that speedometer is properly calibrated.
14. Check engine compression.
15. Check for dragging brakes.

Engine continues to run after ignition is turned off, but runs very rough. If engine runs smoothly, check ignition switch.

Check the following items.

1. Check for binding throttle linkage.
2. Check for leaking injectors. See appropriate component CHART A-7 for that system. Check injector balance.
3. Check IAC system. See DIAGNOSTIC AIDS in appropriate code chart or component CHART C-2 for that system.
4. Check engine for overheating.

A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with amount of acceleration.

Check the following items.

1. Check for obvious overheating problems.
2. Ensure that initial timing is correct.
3. Check TPS adjustment and operation.
4. Check fuel system for low pressure or volume. See appropriate CHART A-7 for that system. Also check for induction air leaks.
5. Ensure that ESC system is operating properly. See appropriate component CHART C-5 for that system.
6. Ensure that EGR valve is not open all the time. See appropriate component CHART C-7 for that system.
7. Ensure that TCC system is operating properly. See appropriate component CHART C-8 for that system.
8. Ensure that correct PROM is installed in ECM.
9. Remove carbon from engine using top engine cleaner.
10. If excessive carbon exists in combustion chamber, check for excessive oil burning due to leaking valve guide seals.
11. Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
12. Check that PROM in vehicle is correct for that vehicle. Check with dealer for latest application information.

Vehicle fails emission test. Vehicle may also have excessive "rotten egg" smell (hydrogen sulfide) being emitted from exhaust pipe.

Check the following items.

1. Perform DIAGNOSTIC CIRCUIT CHECK for that system.
2. Check for lead contamination of catalytic converter. Look for removal/tampering at restrictor in fuel filler neck.
3. If emission test shows excessive carbon monoxide (CO) and hydrocarbons (HC) emissions and vehicle also has excessive odor being emitted, check all systems and components that could cause engine to run rich. See DIAGNOSTIC AIDS in appropriate CODE EO45 chart for that system.
4. If emission test shows excessive oxides of nitrogen (NOx) emissions, check all systems and components that could cause engine to run lean or to run too hot. See DIAGNOSTIC AIDS in appropriate CODE EO44 chart for that system.

REMOVAL & INSTALLATION

STATIC CHARGE (VOLTS)

DIAGNOSTIC CIRCUIT CHECK

The Diagnostic Circuit Check is an organized approach to identifying a problem created by an electronic control system malfunction. If after completing diagnostic circuit check and finding on-board diagnostics functioning properly (with no trouble codes displayed), a comparison of "Typical Scan Values", for the appropriate engine, may be used for comparison. The "Typical Values" are an average of display values recorded from normal operating vehicles and are intended to represent what a normal functioning system would display.

Diagnostic Circuit Check Flow Chart. Scheme 7

Chart A-1, Wiring Diagram "Service Engine Soon" Light Inoperative. Scheme 8

The "SERVICE ENGINE SOON" light is attached to the IPC. It is powered by ignition "3" circuit No. 39. The ECM completes the ground to turn the light on. The light will be on while engine is not running. With the engine running, a steady light indicates an ECM code is set. When the engine is running and diagnostics are entered, a flashing light indicates the field service mode of the ECM. The system monitor button will not affect the "SERVICE ENGINE SOON" light.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step splits the circuit into 2 sections. A light on after grounding terminal "D", indicates the open is on ECM side of split. A light off, indicates the open is on IPC side of circuit.
2. If test light did not illuminate when connected between ECM terminal "BA6" and ground, ECM will not be powered up. This is a result of an open or short to ground (blown fuse) in circuit No. 439.
3. This test checks if open is in IPC or circuit No. 419. There should be battery voltage at IPC terminal "D2" when connected to terminal "C9" ("RBA" and "LT1" on Reatta and Riviera). Test light should illuminate, indicating circuit No. 419 is complete through ALDL terminal "D" which has been jumpered to ground.
4. This test checks if open is in ECM or circuit No. 419. If test light illuminates when ECM terminal "YC11" is grounded, fault is in a poor terminal contact or a faulty ECM.

Chart A-1, Flow Chart "Service Engine Soon" Light Inoperative. Scheme 9

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside insulation. Check for the following

1. Poor Connection Check at ECM pin "YC11" or IPC connector. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connections.
2. Damaged Harness Inspect harness for damage. If harness appears okay, observe related connectors and wiring harness. A flickering light would indicate the intermittent fault location.

Diagnostic Aids Wiring Diagram. Scheme 10

Diagnostic Aids Flow Chart. Scheme 11

CHART A-2, "SERVICE ENGINE SOON" LIGHT WON'T GO OUT

The "SERVICE ENGINE SOON" light is attached to the IPC. It is powered by ignition "3" circuit No. 39. The ECM completes the ground to turn light on. The light will illuminate while engine is not running. With engine running, a steady light indicates an ECM code is set. When engine is running and diagnostics are entered, a flashing light indicates the field service mode of ECM. The system monitor button will not affect the "SERVICE ENGINE SOON" light.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step verifies that light remains on with engine running and no ECM codes displayed.
2. Unplugging ECM harness connector (Yellow) determines if a short to ground exists in the ECM or somewhere else in circuit. If "SERVICE ENGINE SOON" light remains on, fault is not in ECM.
3. This step removes the IPC to distinguish between a grounded IPC or a grounded circuit No. 419. If test light is illuminated when connected between IPC terminals "C9" and "D2" ("RBA" and "LT1" on Reatta and Riviera), circuit No. 419 is shorted to ground.

Chart A-2, Wiring Diagram "Service Engine Soon" Light Won't Go Out. Scheme 12

Chart A-2, Flow Chart "Service Engine Soon" Light Won't Go Out. Scheme 13

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside insulation. Check for the following

1. Poor Connection Check at ECM pin "YC11" or IPC connector. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connections.
2. Damaged Harness Inspect harness for damage. If harness appears okay, observe related connectors and wiring harness. A flickering light would indicate intermittent fault location.

Diagnostic Aids Flow Chart. Scheme 14

CHART A-3, ENGINE CRANKS BUT WILL NOT RUN

The C(3)I system uses waste spark method of spark distribution. In this type of ignition system, ignition module triggers No. 1 and 4 coil, resulting in both No. 1 and 4 spark plugs firing simultaneously. The No. 1 cylinder is on compression stroke at the same time that No. 4 is on 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. The sequential fuel injection type of fuel delivery system utilizes 6 separate injector "driver" circuits to activate 6 fuel injectors. While cranking, ECM activates all 6 injector "driver" circuits simultaneously. After a calibrated engine RPM is reached, and a good camshaft signal has been received by ECM, the injection mode of operation is changed to sequential (sprayed in spark plug firing order).

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

Chart A-3, Wiring Diagram Engine Cranks But Will Not Run (1 of 4). Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

1. This test verifies that "SES" light operation, TPS and coolant sensor signals are normal. A blinking injector test light verifies that ECM is monitoring C(3)I reference signal and attempting to pulse injectors.
2. The crank sensor has been verified as functioning properly. Performing a fuel pressure test will differentiate between fuel related or ignition system problem.
3. By testing for spark on plug leads 1, 3 and 5, each ignition coil's ability to produce at least 25,000 volts is verified. If engine starts, runs for several seconds and dies repeatedly, consider this to be no spark at all.
4. Checking faulty coil's control circuit using a test light, will determine whether coil is faulty, or module's internal driver for that coil is at fault.
5. This test checks for battery voltage at circuit No. 639. If voltage was present, "light off" test result was caused by no activation pulse reaching injector connector from ECM.
6. If fuse was blown, check circuit No. 839, which includes fuel pump relay, fuel pump and wiring, to determine cause of high current flow.
7. Test light to 12 volts simulates a reference signal to ECM. This results in an injector test light flash with each contact of test light probe to terminal "D". It may take up to 3 probe contacts to flash test light. If test light flashes, circuit No. 430, ECM and injector driver circuits are functioning properly.
8. If crank sensor signal circuit terminal "A" is momentarily jumpered to ground circuit terminal "C", and engine is cranked without turning ignition off, the response should be an injector test light flash. The ignition module will then transmit fuel control signal to ECM while cranking. Allowing generation of reference signal to ECM terminal "BD8", and ECM to activate injector driver circuit.
9. This test verifies proper sync-signal circuit voltage of 9-12 volts, and a proper ground from C(3)I module to terminal "C" of sensor connector.
10. Determines if reason for incorrect voltage reading was due to fault in circuit No. 645 or faulty C(3)I module.
11. Jumping crank sensor harness terminals "A" and "C" together, simulates a sync signal to ignition module. By jumpering crank sensor harness terminals "B" and "C" together, a crank signal is simulated. This signal will then cause ECM to energize fuel pump relay for 2 seconds (it should click on and off) and injectors should be heard clicking on and off.
12. Verifies a proper crank signal circuit voltage of 9-12 volts and a good ground from ignition module to terminal "C" of sensor connector.
13. Determines if reason for incorrect voltage reading was due to a fault in circuit No. 643, an open in circuit No. 645, or a faulty ignition module. (Scheme 16): Chart A-3, Flow Chart Engine Cranks But Will Not Run (1 of 4) (Scheme 17): Chart A-3, Flow Chart Engine Cranks But Will Not Run (2 of 4) (Scheme 18): Chart A-3, Flow Chart Engine Cranks But Will Not Run (3 of 4) (Scheme 19): Chart A-3, Flow Chart Engine Cranks But Will Not Run (4 of 4)

CHART A-5, FUEL SYSTEM ELECTRICAL TEST

When ignition is turned on, ECM will energize fuel pump relay, which completes circuit to in-tank fuel pump. It will remain on as long as engine is cranking or running, and ECM is receiving C(3)I reference pulses. If there are no reference pulses, ECM will de-energize fuel pump relay within 2 seconds after key is turned on and engine is not running.

The fuel pump will deliver fuel to fuel rail and injectors, then to pressure regulator, where system pressure is controlled. Excess fuel pressure is by-passed back to fuel tank. When engine is shut off, fuel pump can be turned on by applying battery voltage to test terminal located in engine compartment. Improper fuel system pressure may contribute to one or all of the following symptoms

1. Cranks but won't run.
2. Code EO44 or EO45.
3. Cuts out, may feel like ignition problem.
4. Hesitation, loss of power or poor fuel economy.

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

Chart A-5, Wiring Diagram Fuel System Electrical Test (1 of 2). Scheme 20

Scheme 21

Scheme 22

1. If fuse is blown, a short to ground in circuits No. 120 and 639, or fuel pump itself is cause of problem.
2. Determines if fuel pump circuit is being controlled by ECM. The ECM should energize fuel pump relay. When engine is not cranking or running with key on, ECM should de-energize relay within 2 seconds after ignition is turned on.
3. This test activates fuel pump if circuit No. 120 wiring is okay. If pump runs, problem is basic fuel delivery.
4. This test will determine if a short to ground in circuit No. 120 caused fuse to blow. To prevent an incorrect diagnosis, ensure fuel pump is disconnected before test.
5. Checks for short to ground in fuel pump relay harness circuit No. 639.
6. Checks for open in fuel pump relay ground, circuit No. 450.
7. Determines if ECM is in control of fuel pump relay through circuit No. 465 (terminal "A").
8. The fuel pump control circuit includes an engine oil pressure switch with a separate set of normally open contacts. The switch closes at about 4 psi of oil pressure and provides a second battery voltage feed path to fuel pump. If relay fails, fuel pump will operate using battery voltage supplied by closed oil pressure switch. This step checks oil pressure switch, ensuring that it provides battery voltage to fuel pump should pump relay fail. A failed fuel pump relay will result in extended engine crank time, because of time required to build sufficient oil pressure to close oil pressure switch, and activate fuel pump. There may be circumstances when relay has failed, but engine will not crank fast enough to build sufficient oil pressure to close switch. This, or a faulty oil pressure switch, can result in an "Engine Cranks But Won't Run" condition. (Scheme 21): Chart A-5, Flow Chart Fuel System Electrical Test (1 of 2) (Scheme 22): Chart A-5, Flow Chart Fuel System Electrical Test (2 of 2)

CHART A-7, FUEL PRESSURE TEST

The fuel pump will deliver fuel to fuel rail and injectors and then to pressure regulator, where system pressure is controlled. Excess fuel pressure is by-passed back to fuel tank. The fuel pump test terminal is located in the engine compartment. Fuel pump can be turned on by applying battery voltage to test terminal.

Improper fuel system pressure may contribute to one or all of the following symptoms

1. Cranks but won't run.
2. Code 44 or 45.

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

1. Disconnect negative battery terminal to avoid possible fuel discharge if an accidental attempt is made to start engine.
2. Loosen filler cap in order to relieve tank vapor pressure.
3. Install Fuel Pressure Gauge (J-34730-1) to pressure tap. Wrap a shop towel around fuel pressure gauge tap to absorb any small amount of fuel leakage that may occur when installing gauge.
4. Install bleed hose into an approved container and open valve to bleed system pressure. Fuel connections are now safe for servicing.
5. Drain any fuel remaining in gauge, into an approved container. NOTE: Test numbers refer to test numbers on diagnostic chart.

Scheme 23

Scheme 24

1. Start engine. With ignition on and engine running, pump pressure is regulated by spring pressure and throttle body vacuum within pressure regulator assembly. Turn ignition off for 10 seconds. Pressure should not leak down after fuel pump is shut off.
2. When engine is idling, vacuum is high and is applied to fuel pressure regulator diaphragm. This will overcome regulator spring pressure, resulting in a lower fuel pressure.
3. The application of 12-14 in. Hg vacuum to pressure regulator should result in reduced fuel pressure.
4. Fuel pressure that leaks down may be caused by one of the following conditions: In-tank fuel pump check valve not holding. Pump coupling hose leaking. Fuel pressure regulator valve leaking. Injector sticking open. (Scheme 23): Chart A-7, Flow Chart Fuel Pressure Test (1 of 2) Improper fuel system pressure may contribute to one or all of the following symptoms: Cranks but won't run. Code EO44 or EO45. Cuts out, may feel like ignition problem. Cuts out, may feel like ignition problem. Hesitation, loss of power or poor fuel economy.
5. If fuel system has pressure, but is less than specification, condition may be caused by one of the following: Regulated pressure, but less than specification. The amount of fuel to injectors is okay, but pressure is too low. The fuel system will operate lean and may set Code EO44. Also, hard starting cold and overall poor performance condition may exist. Restricted fuel flow causing pressure drop. Normally, vehicle with fuel pressure of less than 24 psi (1.7 kg/cm 2 ) at idle will not be driveable. If pressure drop occurs only while driving, engine will normally surge and shut off as pressure begins to drop rapidly.
6. Restricting fuel return line allows fuel pump to develop its maximum pressure (dead head pressure). When battery voltage is applied to pump test terminal, pressure should be greater than 75 psi (5.2 kg/cm 2 ).
7. This test determines if high fuel pressure is due to a restricted fuel return line or a pressure regulator problem. (Scheme 24): Chart A-7, Flow Chart Fuel Pressure Test (2 of 2)

Chart B-1, Restricted Exhaust System Check. Scheme 25

Before any components are replaced, exhaust system must be checked for restrictions. Check at O2 sensor procedure may be used to diagnose condition.

1. Raise engine speed to 2500 RPM and observe exhaust system backpressure gauge. Reading should not exceed 1.25 psi (.09 kg/cm 2 ).
2. If during step 1) , specification is exceeded, exhaust system restriction is indicated.
3. Check complete exhaust system for collapsed pipe, heat distress and possible internal muffler failure.
4. If none of the conditions in step 4) exist, check for restricted catalytic converter. Replace if necessary.

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 injector for a precise amount of time, spraying a measured amount of fuel in 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 (J34730-3) 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 in ECM/BCM THEORY & OPERATION section.

Chart C-2, Wiring Diagram Idle Air Control (IAC) Valve Check. Scheme 26

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 condition is unchanged, 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. Probe terminals to check for this condition.

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 the engine has another source of air to intake manifold, ECM will compensate by extending IAC. IAC counts may be zero as the ECM tries to maintain desired idle. For other causes 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. This may also set Code EO45.
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.
4. See TROUBLE SHOOTING in ECM/BCM THEORY & OPERATION.

Chart C-2, Flow Chart Idle Air Control (IAC) Valve Check. Scheme 27

Chart C-3, Wiring Diagram Canister Purge Check. Scheme 28

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 30 seconds.
2. Coolant temperature more than 158°F (60°C).
3. "Closed Loop" operation. 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, Flow Chart Canister Purge Check. Scheme 29

Chart C-4F-1, Wiring Diagram C(3)I Misfire At Idle. Scheme 30

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. If ignition coils are carbon tracked, the coil tower spark plug wire nipples may be damaged.
4. By checking secondary resistance, a coil with an open secondary may be located.
5. By installing a normally operating coil pack, a determination can be made as to fault being the coil or ignition module.

Scheme 31

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

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

1. If misfire problem exists at idle only, see CHART C-4F-1.
2. 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.
3. If ignition coils are carbon tracked, coil tower spark plug wire nipples may be damaged.
4. By installing a normally operating coil, a determination can be made as to the fault being the coil or ignition module.

Scheme 32

Scheme 33

Chart C-5, Wiring Diagram Electronic Spark Control (ESC) System Check. Scheme 34

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 a 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. Also see TROUBLE SHOOTING in ECM/BCM THEORY & OPERATION.

Chart C-5, Flow Chart Electronic Spark Control (ESC) System Check. Scheme 35

Chart C-7, Wiring Diagram Exhaust Gas Recirculation (EGR) Flow Check. Scheme 36

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 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, Flow Chart Exhaust Gas Recirculation (EGR) Flow Check. Scheme 37

Chart C-8A, Wiring Diagram Torque Converter Clutch (TCC). Scheme 38

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

1. "LO" display confirms that 4th gear switch is closed.
2. At 45 MPH, 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. Solenoids are turned on or off by ECM internal electronic switches, called "drivers". Each driver is part of a group of 4, called Quad-Drivers. Using an ohmmeter, check solenoid coil resistance of TCC. Coil resistance must measure greater than 20 ohms.

Chart C-8A, Flow Chart Torque Converter Clutch (TCC). Scheme 39

Chart C-12A, Wiring Diagram Coolant Fan Check (Riviera & Toronado). Scheme 40

All applications use 2 fans and 3 relays.

1. Low Speed The low speed coolant fan relay is energized by the ECM. The ECM will energize the low speed relay when coolant temperature exceeds 208°F (101°C) or when requested to do so by BCM, based on an A/C high side temperature, BCM data BD27, which exceeds 122°F (50°C).
2. High Speed The high speed coolant fan relay is energized by the ECM. The ECM will energize both high speed relays when coolant temperature exceeds 226°F (108°C) or when requested to do so by BCM based on an A/C high side temperature, BCM data BD27, which exceeds 149°F (65°C). 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 Code EO09 grounds "LO" speed relay through ECM for 3 seconds on, and 3 seconds off. "LO" speed fan should be on for 3 seconds and off for 3 seconds.
3. ECM Code EO10 grounds high speed relay through ECM for 3 seconds on and 3 seconds off. High speed fan should be on for 3 seconds and off for 3 seconds.

Chart C-12A, Flow Chart Coolant Fan Check (Riviera & Toronado). Scheme 41

CHART C-12B, COOLANT FAN CHECK (RIVIERA & TORONADO)

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

1. Test light should illuminate, as harness terminal No. 2 has battery voltage with ignition switch in "ON" position. Terminal No. 4 has battery voltage at all times.
2. Test light should illuminate for 3 seconds and turn off for 3 seconds, as Code 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. Cycling of the test light verifies circuit No. 532 and 804 are okay.

Chart C-12B, Flow Chart Coolant Fan Check (Riviera & Toronado). Scheme 42

CHART C-12C-A, COOLANT FAN CHECK NO HIGH SPEED REAR FAN (REATTA, RIVIERA & TORONADO)

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

1. Test light should be on, as harness terminal No. 5 has battery voltage with ignition switch in "ON" position. Terminal No. 1 has battery voltage at all times.
2. Test light should be on for 3 seconds and off for 3 seconds, as Code 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. Cycling of the test light verifies circuits No. 533 and 804 are okay, indicating fan motor is faulty.

Chart C-12C-A, Flow Chart Coolant Fan Check No High Speed Rear Fan (Reatta, Riviera & Toronado). Scheme 43

CHART C-12C-B, COOLANT FAN CHECK NO HIGH SPEED FRONT FAN (RIVIERA & TORONADO)

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

1. Test light should be illuminated, as harness terminal No. 5 has battery voltage with ignition switch turned to "ON" position. Terminal No. 1 has battery voltage at all times.
2. Test light should be illuminated for 3 seconds and turn off for 3 seconds as Code 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. Cycling of test light indicates circuits No. 533 and 804 are okay.

Chart C-12C-B, Flow Chart Coolant Fan Check No High Speed Front Fan (Riviera & Toronado). Scheme 44

CHART C-12D, COOLANT FAN CHECK "ON" AT ALL TIMES (RIVIERA & TORONADO)

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

1. Checks to see if circuits No. 535 or 536 are shorted to ground, which would cause fan relay(s) to be energized at all times.
2. High temperature will cause A/C high side temperature sensor, due to A/C system temperature, to exceed the 122°F (50°C) point and BCM will request low speed fan at all times.
3. Coolant fans will come on when engine is started, but should go off when system stabilizes. Coolant fans should be off when A/C high side temperature switch is disconnected and coolant temperature is less than 208°F (98°C).

Coolant fans should be off if coolant temperature is less than 208°F (98°C) and/or if A/C high side temperature is less than 122°F (50°C). Disconnecting A/C high side temperature sensor should result in BD27 reading less than -30°C. If not, see BCM Code B111 for diagnosis. Disconnecting coolant temperature sensor should cause BD21 to read less than -30°C also. If not, see ECM Codes EO14 or EO15. BD27 should read about 122°F (50°C) when A/C system high side pressure is about 160 psi. Comparing these might indicate defective sensor.

Chart C-12D, Flow Chart Coolant Fan Check "On" At All Times (Riviera & Toronado). Scheme 45

Chart C-12A, Wiring Diagram Coolant Fan Check (Reatta). Scheme 46

All applications use 2 fans and 3 relays.

1. Low Speed The low speed coolant fan relay is energized by the ECM. The ECM will energize the low speed relay when coolant temperature exceeds 208°F (101°C) or when requested to do so by BCM, based on an A/C high side temperature, BCM data BD27, which exceeds 122°F (50°C).
2. High Speed The high speed coolant fan relay is energized by the ECM. The ECM will energize both high speed relays when coolant temperature exceeds 226°F (108°C) or when requested to do so by BCM based on an A/C high side temperature (BD27), which exceeds 149°F (65°C). 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 Code EO09 grounds "LO" speed relay through 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 ALDL terminal "A" to "B" will cause ECM to ground fan relays "G", "C" and "D" through the ECM. Fans should run at high speed.

Chart C-12A, Flow Chart Coolant Fan Check (Reatta). Scheme 47

Chart C-12B, Wiring Diagram Coolant Fan Check (Reatta). Scheme 48

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

1. Test light should illuminate, as harness terminal No. 2 has battery voltage with ignition switch in "ON" position. Terminal No. 4 has battery voltage at all times. Test light on validates circuit through both fan motors, relay "C" and ground connections.
2. Jumpering harness terminals No. 1 to 4 of relay "G" and removing relay "C", and touching a test light to terminal No. 1, validates circuit up to relay "C". If test light is off, circuit No. 532XX, 533XX or front fan is at fault.
3. Test light on validates all circuits. If light is on, relay "C" is faulty. If light is off, connections at rear fan or fan motor is faulty.

Chart C-12B, Flow Chart Coolant Fan Check (Reatta). Scheme 49

CHART C-12C-B, COOLANT FAN CHECK NO HIGH SPEED FRONT FAN (REATTA)

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

1. Test light should be illuminated, as harness terminal No. 2 has battery voltage with ignition switch turned to "ON" position. Terminal No. 4 has battery voltage at all times. Test light on validates circuit through both fan motors, relay "C" and ground connections.
2. Jumpering harness terminals No. 1 to 4 of relay "G" and removing relay "C", and touching test light to terminal No. 1, validates circuit up to relay "C". If test light is off, circuit 532XX, 533XX or front fan is at fault.
3. If test light is on, all circuits are validated. This indicates relay "C" is faulty. If test light is off, a problem with ground circuit No. 804 exist.

Chart C-12C-B, Wiring Diagram Coolant Fan Check No High Speed Front Fan (Reatta). Scheme 50

Chart C-12C-B, Flow Chart Coolant Fan Check No High Speed Front Fan (Reatta). Scheme 51

Chart C-12D, Wiring Diagram Coolant Fan Check "On" At All Times (Reatta). Scheme 52

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

1. Fans should not run when ignition key is off.
2. Fans should not run when engine is off.
3. Disconnecting A/C high side temperature sensor will remove ECM/BCM request, due to A/C high side temperature.
4. Defines fan operation based on coolant temperature only.

Coolant fans should be off if coolant temperature is less than 208°F (98°C) and/or if A/C high side temperature is less than 122°F (50°C). Disconnecting A/C high side temperature sensor should result in BD27 reading less than -30°C. If not, see BCM Code B111 for diagnosis. Disconnecting coolant temperature sensor should cause BD21 to read less than -30°C also. If not, see ECM Codes EO14 or EO15. BD27 should read about 122°F (50°C) when A/C system high side pressure is about 160 psi. Comparing these might indicate defective sensor.

Chart C-12D, Flow Chart Coolant Fan Check "On" At All Times (Reatta). Scheme 53

Self-Diagnostic System Check (Reatta & Riviera). Scheme 54

Chart B-1, Cannot Enter Diagnostics (Reatta & Riviera). Scheme 55

Chart B-2, Wiring Diagram CRTC Or Data Problem (Reatta & Riviera). Scheme 56

Chart B-2, Flow Chart CRTC Or Data Problem (Reatta & Riviera). Scheme 57

Chart B-3, No Communication (Reatta & Riviera). Scheme 58

Chart B-4, No Communication (Reatta & Riviera). Scheme 59

Chart B-5, CRTC Problem (Reatta & Riviera). Scheme 60

Chart B-6, No Communication To IPC With Only Radio Functions (Reatta & Riviera). Scheme 61

Chart B-7, Wiring Diagram BCM Problem (Reatta & Riviera). Scheme 62

Chart B-7, Flow Chart BCM Problem (Reatta & Riviera). Scheme 63

CHART B-8, Loss Of Logic - 7 Volts (Reatta & Riviera). Scheme 64

Chart C-1, CRT Problem (Reatta & Riviera). Scheme 65

Chart C-2, Wiring Diagram No Picture (Reatta & Riviera). Scheme 66

Chart C-2, Flow Chart No Picture (Reatta & Riviera). Scheme 67

Chart C-3, No Switches Respond Or Beeper Problem (Reatta & Riviera). Scheme 68

Chart C-4, Some Switches Do Not Respond (Reatta & Riviera). Scheme 69

Chart C-5, Picture Rolls (Reatta & Riviera). Scheme 70

Self-Diagnostic System Check (Toronado CRT Equipped). Scheme 71

Chart A, Wiring Diagram Loss Of IPC Display (Toronado CRT Equipped). Scheme 72

Chart A, Flow Chart Loss Of IPC Display (Toronado CRT Equipped). Scheme 73

Chart A-1, Wiring Diagram CPS Check (Toronado CRT Equipped). Scheme 74

Chart A-1, Flow Chart CPS Check (Toronado CRT Equipped). Scheme 75

Chart B, Wiring Diagram Color CRT Blank With Ignition On (Toronado CRT Equipped). Scheme 76

Chart B, Flow Chart Color CRT Blank With Ignition On (Toronado CRT Equipped). Scheme 77

Chart D-1, Wiring Diagram Serial Data Circuit Open (Toronado CRT Equipped). Scheme 78

Chart D-1, Flow Chart Serial Data Circuit Open (Toronado CRT Equipped). Scheme 79

Chart D-2, Wiring Diagram Grounded Serial Data Circuit (Toronado CRT Equipped). Scheme 80

Chart D-2, Flow Chart Grounded Serial Data Circuit (Toronado CRT Equipped). Scheme 81

Chart D-3, Wiring Diagram Serial Data Circuit Shorted (Toronado CRT Equipped). Scheme 82

Chart D-3, Flow Chart Serial Data Circuit Shorted (Toronado CRT Equipped). Scheme 83

Chart E, Wiring Diagram Color CRT Abnormalities (Toronado CRT Equipped). Scheme 84

Note. If have not performed the self-diagnostic system check, start there first

CHART E, COLOR CRT ABNORMALITIES

Note. When All Diagnosis and Repair are Completed, Clear Codes and Verify Operation

Self-Diagnostic System Check (Toronado ECC Equipped). Scheme 85

Chart A, Wiring Diagram Loss Of IPC Display (Toronado ECC Equipped). Scheme 86

Chart A, Flow Chart Loss Of IPC Display (Toronado ECC Equipped). Scheme 87

Chart A-1, CPS Check (Toronado ECC Equipped). Scheme 88

Chart B, Wiring Diagram Loss Of Serial Data (Toronado ECC Equipped). Scheme 89

Chart B, Flow Chart Loss Of Serial Data (Toronado ECC Equipped). Scheme 90

Chart C, Loss Of ECC Communications (Toronado ECC Equipped). Scheme 91

Chart D, Loss OF Communication (Toronado ECC Equipped). Scheme 92

Chart D-1, Serial Data Circuit Open (Toronado ECC Equipped). Scheme 93

Chart D-2, Grounded Serial Data Circuit (Toronado ECC Equipped). Scheme 94

Chart D-3, Serial Data Circuit Short (Toronado ECC Equipped). Scheme 95

Code B110, Wiring Diagram Outside Temperature Sensor Circuit. Scheme 96

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

Code B110 will set if ignition is on and 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 time failure is present, a substitute temperature reading will be used to allow continued operation of the climate control system, and continuous compressor at idle will be disabled. The outside air temperature reading BD26 display will indicate the actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

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

Note On Intermittents

If ambient temperature drops to less than about -31°F (-35°C), this code should be ignored. If B110 is set with any of the following codes: B119, B120, B122, B132 or B440, the most likely cause is an intermittent open circuit No. 736.

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

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

Code B110, Flow Chart Outside Temperature Sensor Circuit. Scheme 97

Code B111, Wiring Diagram A/C High Side Temperature Sensor Circuit. Scheme 98

Code B111, Wiring Diagram A/C High Side Temperature Sensor Circuit. Scheme 99

The A/C high side temperature sensor is a thermistor that controls signal voltage to BCM. The BCM applies and monitors voltage on circuit No. 732 to sensor. When sensor is cold, its resistance is high, therefore, BCM will see a high monitored voltage. As sensor warms, resistance becomes less and signal voltage is pulled low through 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 ignition is on, outside temperature sensor has not failed and reads greater than 32°F (0°C), and signal voltage indicates less than -24°F (33°C), which is open circuit voltage or greater than 408°F (209°C), which is shorted circuit voltage. During time failure is present, a substitute temperature reading will be used to allow continued operation of climate control system. The A/C high side temperature reading BD27 display will indicate actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

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

If Code B111 is set with Code B112, check for an intermittent open in circuit No. 736 between splice "S1" and "S2". If an intermittent Code B111 is being set, check Code B111 snap data value for high side temperature, BD27 display. If BD27 display value is less than -33°C, code was caused by an open in circuit No. 732, circuit No. 736 or high side temperature sensor. If BD27 display is greater than 209°C, code resulted from a short to ground on circuit No. 732 or a shorted high side temperature sensor. Manipulate related wiring while observing BD27 display. If failure is induced, reading will jump from its normal value to a reading outside the range of -24°F (-33°C) to 409°F (209°C).

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

Code B111, Flow Chart A/C High Side Temperature Sensor Circuit. Scheme 100

Code B112, Wiring Diagram (1 of 2) A/C Low Side Temperature Sensor Circuit. Scheme 101

Code B112, Wiring Diagram (2 of 2) A/C Low Side Temperature Sensor Circuit. Scheme 102

The A/C low side temperature sensor is a thermistor that controls signal voltage to BCM. The BCM applies and monitors voltage on circuit No. 731 to sensor. When sensor is cold, its resistance is high, therefore, BCM will see a high monitored voltage. As sensor warms, its resistance becomes less and signal voltage is pulled low through 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 ignition is on, outside temperature sensor has not failed and reads greater than 32°F (0°C), and 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 time failure is present, a substitute temperature reading (same value as outside air temperature) will be used to allow continued operation of climate control system and compressor clutch will be disabled. The A/C low side temperature reading BD28 display will display actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

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

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

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

Code B112, Flow Chart A/C Low Side Temperature Sensor Circuit. Scheme 103

Code B113, Wiring Diagram (Riviera & Reatta) In-Car Temperature Sensor Circuit. Scheme 104

The in-car temperature sensor is a thermistor that controls signal voltage to BCM. The BCM applies and monitors voltage on circuit No. 734 to sensor. When sensor is cold, its resistance is high, therefore, BCM will see a high monitored voltage. As sensor warms, its resistance becomes less and monitored voltage is pulled low through 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 ignition is on, outside temperature sensor has not failed and reads greater than 32°F (0°C), and 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 time failure is present, a substitute temperature reading will be used to allow continued operation of climate control system. The in-car temperature reading BD25 display will indicate actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

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

If Code B113 is set with Code B115, check for an intermittent open in circuit No. 736 between splice "S2" and Instrument Panel (IP)-to-dash transition block. If an intermittent Code B113 is being set, manipulate related wiring while observing BD25 display. If failure is induced, reading will jump from its normal value to a reading outside the range of -29°F (-34°C) to 209°F (85°C).

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

Code B113, Wiring Diagram In-Car Temperature Sensor Circuit (Toronado). Scheme 105

Code B113, Flow Chart In-Car Temperature Sensor Circuit. Scheme 106

Code B115, Wiring Diagram (Reatta & Riviera) Sun Load Sensor Circuit. Scheme 107

Code B115, Wiring Diagram (Toronado) Sun Load Sensor Circuit. Scheme 108

The sun load sensor is a thermistor that controls signal voltage to BCM. The BCM applies and monitors voltage on circuit No. 590 to sensor. When sensor is cold, its resistance is high, therefore, BCM will see a high monitored voltage. As sensor warms, its resistance becomes less and monitored voltage is pulled low through 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 ignition is on, outside temperature sensor has not failed and reads greater than 32°F (0°C), and 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 time failure is present, a substitute temperature reading will be used to allow continued operation of climate control system. The sun load temperature reading BD32 display will indicate actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

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

If an intermittent Code B115 is being set, check B115 snap data value for sunload temperature, BD32 display. If BD32 display value is less than -34°C, code resulted from an open in circuit No. 590, circuit No. 736 or sun load temperature sensor. If BD32 display value is greater than 85°C, code resulted from a short to ground on circuit No. 590 or shorted sunload temperature sensor. Manipulate related wiring while observing BD32 display. If failure is induced, reading will jump from its normal value to a reading outside the range of -29°F (-34°C) to 209°F (85°C).

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

Code B115, Flow Chart Sun Load Sensor Circuit. Scheme 109

Code B119, Wiring Diagram (1 of 2) Twilight Photocell Circuit. Scheme 110

Note. Ensure nothing is covering sensor before following this procedure.

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

Code B119 will set if ignition is on and signal voltage indicates more than 97 percent, open circuit voltage or less than 3 percent, which is shorted circuit voltage). During time failure is present, a substitute light reading (indicating darkness) will be used to allow continued operation of headlights. The measure of light reading, BD44 display, will indicate actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

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

Code B119, Wiring Diagram (2 of 2) Twilight Photocell Circuit. Scheme 111

If an intermittent Code B119 is being set, manipulate related wiring while observing BD44 display. If failure is induced, reading will jump from its normal value to a reading outside the range of 3-97 percent. Make certain owner is aware not to cover sensor.

Code B119, Flow Chart Twilight Photocell Circuit. Scheme 112

CODE B120, TWILIGHT DELAY POTENTIOMETER (REATTA & RIVIERA)

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

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

Note. Test numbers refer to numbers on diagnostic chart.

1. BD43 displays twilight delay time. The normal range is 2-98 percent.
2. Checks to see if open or grounded circuit reading is due to circuit or switch. If open or grounded circuit reading changes from a short to voltage reading after jumping switch assembly terminals, BCM and wiring are okay.
3. Measuring between circuit No. 705 (5 volts) and circuit No. 736 will determine if circuits No. 705 or 271 is open or shorted to ground.

Code B120, Wiring Diagram (1 of 2) Twilight Delay Potentiometer (Reatta & Riviera). Scheme 113

Code B120, Wiring Diagram (2 of 2) Twilight Delay Potentiometer (Reatta & Riviera). Scheme 114

If an intermittent Code B120 is being set, check B120 snap data value for twilight delay BD43 display. If BD43 display value is greater than 98 percent, code resulted from an open in circuit No. 271, circuit No. 736 or left switch pod. If BD43 display value is less than 2 percent, code resulted from a short in left switch pod. Manipulate related wiring while observing BCM data parameter BD43 display. If failure is induced, reading will jump from its normal value to a reading outside range of 2-98 percent.

Code B120, Flow Chart Twilight Delay Potentiometer (Reatta & Riviera). Scheme 115

CODE B120, TWILIGHT DELAY POT CIRCUIT (TORONADO)

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

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

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if open or grounded circuit reading is due to circuit or switch. If open or grounded circuit reading changes from a short to voltage reading after jumping switch assembly terminals, BCM and wiring are okay.
2. Measuring between circuit No. 705 (5 volts) and circuit No. 271 will determine if circuit No. 271 is open or shorted to ground.
3. Checks to see if short to voltage circuit reading is due to circuit or switch assembly. If a short to voltage reading changes to an open circuit reading after disconnecting switch assembly, BCM and wiring are okay.

If an intermittent Code B120 is being set, check B120 snap data value for twilight delay BD43 display. If BD43 display value is greater than 98 percent, code resulted from an open in circuit No. 271, circuit No. 736 or left switch pod. If BD43 display value is less than 2 percent, code resulted from a short in left switch pod. Manipulate related wiring while observing BD43 display. If failure is induced, reading will jump from its normal value to a reading outside the range of 2-98 percent.

Code B120, Flow Chart Twilight Delay Pot Circuit (Toronado). Scheme 116

Code B120 & B122, Wiring Diagram (Reatta & Riviera) Twilight Delay & Panel Dimming. Scheme 117

Code B120 & B122, Wiring Diagram (Toronado) Twilight Delay & Panel Dimming. Scheme 118

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

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if open or grounded circuit reading is due to circuits or switch assembly. If voltage can be read across circuits No. 705 and 736 after disconnecting switch assembly, BCM and wiring are okay.
2. Checks for 5-volt reference at switch. If 5 volts is present, circuit No. 736 is open. If circuit No. 736 is open, open will be between terminal No. 4 on left switch assembly and cavity "G3" on dash IP transition connector.
3. If circuit No. 705 is suspected of being grounded, remove HVAC programmer and BCM connectors prior to making a ground check.
4. If there is no ground in circuit No. 705, replace HVAC programmer or BCM.

If an intermittent Code B120 & B122 is being set, check B120 snap data value for twilight delay BD43 display. If BD43 display value is greater than 98 percent, code resulted from an open in circuit No. 271, circuit No. 736 or left switch pod. If BD43 display value is less than 2 percent, code resulted from a short in left switch pod. Manipulate related wiring while observing BD43 display. If failure is induced, reading will jump from its normal value to a reading outside the range of 2-98 percent.

Code B120 & B122, Flow Chart Twilight Delay & Panel Dimming. Scheme 119

Code B121, Wiring Diagram Twilight Enable Switch Circuit (Reatta & Riviera). Scheme 120

The twilight enable switch uses the same physical control as delay pot. Inside left switch assembly, enable switch contacts close as soon as time delay slider is moved off of its extreme minimum (off) position. The BCM supplies a voltage on circuit No. 304 to switch. When slider is moved from off position, switch contacts close and signal voltage is pulled low through ground circuit No. 804.

Code B121 will set if vehicle is equipped with twilight sentinel, twilight delay pot has not failed (Code B120), and signal voltage is high when delay slider is greater than 2 seconds delay (twilight sentinel on), or signal voltage is low when delay slider is less than 3 seconds (twilight sentinel off). During time failure is present, twilight sentinel will operate based on delay input. Whenever delay is greater than 2 seconds, BCM will assume twilight sentinel is on.

Note. Test numbers refer to numbers on diagnostic chart.

1. BI82 displays voltage state of circuit at BCM. These conditions can be observed in BI82 display as readings of "HIGH "or "LOW" when slider is moved.
2. Checks to see if "LOW" reading is due to circuit or switch assembly. If display changes from "LOW" to "HIGH" when switch assembly is disconnected, both BCM and wiring are okay.
3. Checks to see if "HIGH" reading is due to circuit or switch assembly. If display changes from "HIGH" to "LOW" after jumping switch assembly terminals, BCM and wiring are okay.

If an intermittent Code B121 is being set, manipulate related. When BI82 displays change-of-state, an "X" will be indicated. Check circuit for an intermittent open or short.

Code B121, Flow Chart Twilight Enable Switch Circuit (Reatta & Riviera). Scheme 121

Code B122, Wiring Diagram Panel Dimming Potentiometer Circuit (Reatta & Riviera). Scheme 122

The panel dimmer is a potentiometer that indicates desired display intensity to BCM. The BCM supplies voltage on circuit No. 705 and a ground on circuit No. 736 to potentiometer in left switch assembly. The wiper provides voltage signal to BCM on circuit No. 686, indicating position of slider and delay time. When slider is moved toward minimum position, its resistance increases and signal voltage decreases.

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

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if open or grounded circuit reading is due to circuits or switch assembly. If open or grounded circuit reading changes to a short to voltage reading, after jumpering switch assembly terminals, BCM and wiring are okay.
2. Measuring voltage between circuit No. 705 (5 volts) and circuit No. 736 will determine if problem is in circuits No. 705 or 686.
3. Checks to see if short to voltage circuit reading is due to circuit or an open in circuit No. 736 and switch assembly. If a short to voltage reading changes to an open circuit reading, after disconnecting switch assembly, BCM and circuit No. 686 are okay.

If an intermittent Code B122 is being set, check B122 snap data value for twilight delay BD42 display. If BD42 display value is greater than 98 percent, code resulted from an open in circuit No. 271, circuit No. 736 or left switch pod. If BD42 display value is less than 2 percent, code resulted from a short in left switch pod. Manipulate related wiring while observing BD42 display. If failure is induced, reading will jump from its normal value to a reading outside the range of 2-98 percent.

Code B122, Flow Chart Panel Dimming Potentiometer Circuit (Reatta & Riviera). Scheme 123

Code B122, Wiring Diagram (Reatta & Riviera) Panel Dimming Switch Pot Circuit. Scheme 124

Code B122, Wiring Diagram (Toronado) Panel Dimming Switch Pot Circuit. Scheme 125

The panel dimmer is a potentiometer that indicates desired display intensity to BCM. The BCM supplies voltage on circuit No. 705 and a ground on circuit No. 736 to potentiometer in left switch assembly. The wiper provides voltage signal to BCM on circuit No. 686, indicating position of slider and delay time. When slider is moved toward minimum position, its resistance increases and signal voltage decreases.

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

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if open or grounded circuit reading is due to circuit or switch assembly. If open or grounded circuit reading changes from a short to voltage reading after jumping switch assembly terminals, BCM and wiring are okay.
2. Measuring voltage between circuit No. 705 (5 volts) and circuit No. 686 will determine if circuit No. 686 is open or shorted to ground.
3. Checks to see if short to voltage reading is due to circuit or switch assembly. If a short to voltage reading changes to an open circuit reading after disconnecting switch assembly, BCM and wiring are okay.

If an intermittent Code B122 is being set, check B122 snap data value for twilight delay BD42 display. If BD42 display value is greater than 98 percent, code resulted from an open in circuit No. 271, circuit No. 736 or left switch pod. If BD42 display value is less than 2 percent, code resulted from a short in left switch pod. Manipulate related wiring while observing BD42 display. If failure is induced, reading will jump from its normal value to a reading outside the range of 2-98 percent.

Code B122, Flow Chart Panel Dimming Switch Pot Circuit (Toronado). Scheme 126

CODE B123, PANEL LAMP SWITCH CIRCUIT

Inside left switch assembly, panel lamp switch contacts close when dimming slider is moved to its extreme maximum position. The BCM supplies a voltage on circuit No. 685 to switch. When signal is pulled to ground, BCM turns courtesy light on.

Code B123 will set if panel dimming pot has not failed and BCM sees circuit No. 685 grounded while 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 courtesy lights on at all times and drain battery.

Note. Test numbers refer to numbers on diagnostic chart.

1. BI01 display, dimmer switch input, will read "LOW" if dimming slider is at maximum "up" position. BI01 display will read "HIGH" if dimming slider is not at maximum position.
2. By removing switch assembly, a shorted switch can be detected by observing BI01 display.
3. By removing BCM connector, short to ground can be isolated as being wire or BCM.

Code B123, Wiring Diagram (1 of 2) Panel Lamp Switch Circuit. Scheme 127

Code B123, Wiring Diagram (2 of 2) Panel Lamp Switch Circuit. Scheme 128

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

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

Code B123, Flow Chart Panel Lamp Switch Circuit. Scheme 129

Code B124, Wiring Diagram Vehicle Speed Sensor (VSS) Circuit Problem. Scheme 130

The vehicle speed sensor uses a Permanent Magnet (PM) generator to generate an electrical signal representative of vehicle speed. This signal is sent to ECM through circuit No. 400 (VSS high) and circuit No. 401 (VSS low), where ECM buffers and amplifies signal. Output voltage of generator can be read by using a digital voltmeter on 2-volt AC scale while rotating generator drive (front wheels). Code B124 will set if following conditions are present for 30 seconds

1. Ignition on.
2. No Code B334.
3. Transaxle in 4th gear.
4. Vehicle speed is zero.
5. Condition occurs for at least 2 seconds.

Or if following conditions exist

1. Ignition on.
2. No Code B334.
3. Vehicle speed is zero.
4. Code B124 currently set.

During time failure is present, cruise control and continuous compressor at idle will be disabled. Vehicle speed reading BD60 display will indicate actual sensor reading.

Note. Test numbers refer to numbers on diagnostic chart.

1. Since ECM amplifies and buffers speed signal before it is sent to BCM, Code EO24 in ECM may set along with Code B124 in BCM. If Code B124 sets with a Code EO24, refer to diagnosis for Code EO24.
2. Since Code EO24 is not set, problem is not actual sensor. Problem must be with ECM, BCM or dedicated speed data line circuit No. 437 between ECM and BCM.

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

Code B124, Flow Chart Vehicle Speed Sensor (VSS) Circuit Problem. Scheme 131

Code B127 Schematic, Gear Selector Switch CKT (Toronado). Scheme 132

The gear selector switch (or PRNDD21) is mounted on transaxle assembly. It is a multi-signal switch sending information relative to gear selector position to BCM and ECM. The PRNDD21 switch assembly also contains neutral safety switch. The PRNDD21 switch uses 4 discrete circuits to pull 4 BCM voltages low in various combinations to indicate each gear range. The voltage level of each of circuits is represented in BD41 display as "0" equals grounded and "1" equals not grounded. The 4 digits displayed represent decoder A, B, C and parity inputs in sequence.

The PRNDD21 switch also provides Park/Neutral inputs to ECM in a similar manner using one discrete input. This can be seen using EI74, where "HI" or "LO" represent voltage level of input terminal. Code B127 will set if following conditions occur

1. PRNDD21 switch input indicates Park/Neutral, but ECM input does not.
2. PRNDD21 switch input does not indicate Park/Neutral, but ECM input does.
3. Decoder and parity inputs do not agree with possible combinations (per BD41 display value chart).

If Code B127 is set, Driver Information Center (DIC) will display warning message "GEAR SELECT FAULT" and IPC PRNDD21 display will flash.

Note. Test numbers refer to numbers on diagnostic chart.

Scheme 133

Scheme 134

Scheme 135

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. Note On Intermittents Manipulate related ECM and BCM wiring in each gear range while looking for a change in BD41 or ED74 display values to check for intermittent open or short to ground. Also check terminals for good contact at ECM, BCM and PRNDD21 switch. If good contact exists and Code B127 continues to set, replace PRNDD21 switch. (Scheme 133): Code B127, Flow Chart (1 of 3) Gear Selector Switch Circuit (Toronado)
5. Checks for short to ground in gear selector switch to BCM circuits.
6. Checks for open in circuits to BCM.
7. Circuit shorted to ground will result in a "0" for circuit.
8. Checks for open PRNDD21 sensor ground.
9. Circuit with open will result in a "1" for circuit. (Scheme 134): Code B127, Flow Chart (2 of 3) Gear Selector Switch Circuit (Toronado)
10. The snap data value of BD41 display will be value that BCM recognized when code was set. This used to determine whether this value is valid. If it is a valid value, ECM Park/Neutral input must be incorrect to set code.
11. If snap value of BD41 display is invalid, it should be determined which of digits are invalid. If all digits read one, PRNDD21 ground is open. If only one digit is incorrect, that circuit, either in switch or harness, was shorted or open when code was set. (Scheme 135): Code B127, Flow Chart (3 of 3) Gear Selector Switch Circuit (Toronado)

Code B132, Wiring Diagram (Reatta & Riviera) Engine Oil Pressure Sensor Circuit Faulty. Scheme 136

Code B132, Wiring Diagram (Toronado) Engine Oil Pressure Sensor Circuit Faulty. Scheme 137

The oil pressure indicator is a variable resistor used to indicate oil pressure to BCM. The BCM supplies voltage on circuit No. 313 to sensor. When the engine is not running (oil pressure low), sensor resistance is low. When the engine is running (increased oil pressure), sensor resistance becomes high. The signal voltage will vary between 5 volts (open circuit) and zero volts (short circuit). Code 132 will set if engine is running and the signal voltage indicates greater than 80 psi for at least 2 seconds. As actual engine oil pressure will never be that high, code indicates an open circuit, faulty sensor or faulty BCM.

Note. Test numbers refer to numbers on diagnostic chart.

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

Code B132, Flow Chart Engine Oil Pressure Sensor Circuit Faulty. Scheme 138

Code B140, Wiring Diagram (1 of 2) Phone System Fault. Scheme 139

Code B140, Wiring Diagram (2 of 2) Phone System Fault. Scheme 140

The BCM receives phone status information directly from the phone transceiver on circuit No. 902 and from CRT controller across serial data line. The phone status input to BCM is a pulse width modulated signal that indicates what state the phone is in. The phone status input from the CRT controller is a discrete indication of whether CRT is able to communicate with the phone transceiver across E & C data line.

Code B140 will set if either of the following sets of conditions are met for more than 2 seconds

1. Code B335 is not set.
2. CRT controller indicates a phone communication failure.

Or phone status input, BD45 is 7, indicating zero percent pulse width signal (a ground).

Note. For diagnosis of Code B140 cellular telephone will require servicing.

Serial Data Circuit Multiple Intermittent Data Codes (Toronado). Scheme 141

Serial Data Flow Chart Circuit Multiple Intermittent Data Codes (Toronado). Scheme 142

Code B332, Wiring Diagram Loss Of Compass Data. Scheme 143

Code B332 will set if communication between the compass and BCM is lost. If Code B332 is set, an "Electrical Problem" message will be displayed and the compass will display the last direction indicated until compass communication resumes.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if other data line components are experiencing communications problems.
2. Checks status of data line at compass module. Normal data line voltage is between .1 and 4.5 volts.

If an intermittent Code B332 is being stored, manipulate the related wiring at compass module and up to splice. An "Electrical Problem" message indicates a loss of data and may help locate fault.

Code B332, Flow Chart Loss Of Compass Data. Scheme 144

Code B334, Wiring Diagram Loss Of ECM Data. Scheme 145

Code B334 will set if communication between ECM and BCM is lost. If the BCM remains powered and only serial communication is lost, the vehicle will still run, with 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, code will set since ECM cannot communicate. It is important to note that engine will not start.
2. Since prior checks eliminated an open circuit, fault is poor terminal contact at ECM terminal "A8", a faulty CALPAK connection or a faulty ECM.

If an intermittent Code B334 is being set, manipulate the related wiring at 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. Also check ECM and CALPAK connections.

Code B334, Flow Chart Loss Of ECM Data. Scheme 146

Code B335, Wiring Diagram (Reatta & Riviera) Loss Of ECC Or CRTC Serial Data. Scheme 147

This code can only be viewed as a history code, because if it was current, service diagnostics could not be entered. Most likely the ECC controls for heating and A/C will also be inoperative when the loss of serial data occurs.

Code B335, Wiring Diagram (Toronado) Loss Of ECC Or CRTC Serial Data. Scheme 148

Since the serial data lines are redundant, a double open in the circuit No. 800 has to occur to set this code. However, the code will also set for a single open in the power or ground supply to the ECC.

Code B335 indicates an intermittent has occurred. Should intermittent problem persist, check the following circuits for opens or poor terminal contacts.

INTERMITTENT PROBLEM CIRCUIT CHECK

CTRC Connector Front View. Scheme 149

If intermittent persists, replace CRTC.

INTERMITTENT PROBLEM CIRCUIT CHECK

ECC Connector Front View. Scheme 150

If intermittent persists, replace ECC Head.

INTERMITTENT PROBLEM CIRCUIT CHECK

If intermittent persists, replace IPC Head.

IPC Connector Front View (1 of 2). Scheme 151

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.

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

INTERMITTENT PROBLEM CIRCUIT CHECK

If intermittent persists, replace IPC.

IPC Connector Front View (2 of 2). Scheme 152

Code B337, Wiring Diagram (Reatta & Riviera) Loss Of HVAC Programmer Data. Scheme 153

Code B337, Wiring Diagram (Toronado) Loss Of HVAC Programmer Data. Scheme 154

Code B337 will set if communication between the programmer and BCM is lost. 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, Flow Chart Loss Of HVAC Programmer Data. Scheme 155

Serial Data, Wiring Diagram Circuit Multiple Intermittent Codes. Scheme 156

Serial Data, Flow Chart Circuit Multiple Intermittent Codes. Scheme 157

Code B410, Wiring Diagram (Reatta & Riviera) Charging System Circuit Fault. Scheme 158

Code B410, Wiring Diagram (Toronado) Charging System Circuit Fault. Scheme 159

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 conditions exist

1. Engine running.
2. Generator enable line is low.

Or if the following conditions exist

1. Engine running.
2. Generator enable line high.
3. Generator field input is less than 2 percent.

Or if the following conditions exist

1. Ignition on, engine not running.
2. Generator enable line is high.

Or if the following conditions exist.

1. Ignition on, engine not running.
2. Generator enable line is low.
3. Generator field input is less than 2 percent.

Code B140 will cause the "Generator Problem" message to be displayed on the DIC and the "NO CHARGE" telltale to light on the IPC.

Note. Test numbers refer to numbers on diagnostic chart.

1. BI51 displays generator signal voltage as "HIGH" or "LOW", depending on the voltage state at 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, BCM and circuit No. 25 are okay.
3. Checks to see if fault is due to BCM or circuit No. 25.
4. BD51 displays the amount of generator field activity. Under normal conditions, a reading less than 7 percent would indicate a fault in field circuit at BCM.
5. Removing the generator connector will determine if fault is due to generator or an open in circuit No. 25, including BCM and interface connector.

If an intermittent condition exists, check B410 snap data parameters BD61 and BI51. Also check for the following conditions

1. If BD61 is under 500 RPM and BI51 is high, check for an intermittent open in circuit No. 25.
2. If BD61 is under 500 RPM and BI51 is low, check for an intermittent short to ground in circuit No. 23.
3. If BD61 is over 500 RPM and BI51 is high, check for an intermittent short to ground in circuit No. 23.
4. If BD61 is over 500 RPM and BI51 is low, check for an intermittent short to ground in circuit No. 25.

Also perform the battery and charging system checks, to ensure proper operation of these components.

Code B410, Flow Chart Charging System Circuit Fault. Scheme 160

Code B411 Or B412, Wiring Diagram (Reatta & Riviera) Battery Voltage Too High Or Too Low. Scheme 161

Code B411 Or B412, Wiring Diagram (Toronado)Battery Voltage Too High Or Too Low. Scheme 162

The BCM monitors ignition 1 voltage on terminal No. 3D7 as a reference for fuel control. Code B411 will set when ignition is on and the engine RPM is greater than 800 and the BCM sees an ignition 1 reference voltage of less than 10.6 volts. Code B412 will be set if the BCM sees voltage over 16 volts. Both B411 and B412 will cause the "Generator Problem" message to be displayed on the IPC.

Note. Test numbers refer to numbers on diagnostic chart.

1. BD50 displays battery voltage. The normal range is 10.6-16 volts.
2. Checks to see if low voltage reading is due to circuit or battery. With engine running, and if voltage is less than 10 volts, BCM and wiring are okay.
3. Checks to see if low voltage reading is due to circuit or BCM. If voltage reading at BCM is less than 10.6 volts, BCM is okay.
4. Checks to see if high voltage reading is due to generator or faulty BCM.
5. Checks to see if charging voltage goes too high with higher engine RPM or electrical load.

If an intermittent Code B411 or B412 is being set, observe BD50 display. This battery voltage reading is monitored from 15-amp ISO IGN 1 fuse, fuel reference voltage. If code is being set due to a high current draw in a certain vehicle component, this can be observed by reading BD50 display. Operate various components while watching for reading to drop to less than 10 volts or increase to greater than 16 volts.

Code B411 Or B412, Flow Chart Battery Voltage Too High Or Too Low. Scheme 163

Code B420, Wiring Diagram Courtesy - Twilight Light Relay Circuits (Riviera & Reatta). Scheme 164

The BCM operates the twilight sentinel (if equipped), retained accessory power, "HI/LO" beam and courtesy lamp relays by providing grounds for coils. When relay(s) are on, BCM output will be low and when relay(s) are off, BCM output will be high. Code B420 will set if output voltage at BCM is high when a low has been commanded, or output voltage is low when high has been commanded. The Reatta will not be equipped with twilight sentinel and only uses one relay for HI/LO beam control.

Note. Test numbers refer to numbers on diagnostic chart.

1. To determine which system has failed (courtesy lamps, twilight, if equipped, "HI/LO" beams, or retained accessory power), select BCM output function in diagnostics. As individual outputs cycle on and off, observe their actual operation.

Since all 4 (or 3 in the case of Reatta) groups of relays can cause an intermittent condition, see NOTE ON INTERMITTENTS (in each CODE B420 Cont.) for each of the relays.

Code B420, Flow Chart Courtesy - Twilight Light Relay Circuits (Riviera & Reatta). Scheme 165

Code B420, Wiring Diagram Courtesy Lamp Relay Circuits (Riviera & Reatta). Scheme 166

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

Note. Test numbers refer to numbers on diagnostic chart.

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

If an intermittent Code B420 is being set. Manipulate related wiring in output function and watch for relays to cycle. Since this code only monitors the control (winding) side of relays, it is possible for the relay to fail and/or circuits on relay contacts. This would prevent courtesy lamp from operating, without setting this code.

Code B420, Flow Chart Courtesy Lamp Relay Circuits (Riviera & Reatta). Scheme 167

Code B420, Wiring Diagram Twilight Relay Circuits (Optional On Riviera Only). Scheme 168

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

Note. Test numbers refer to numbers on diagnostic chart.

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

If an intermittent Code B420 is being set. Manipulate related wiring in output function and watch for relays to cycle. Since this code only monitors the control (winding) side of relays, it is possible for the relay to fail and/or circuits on relay contacts. This would prevent courtesy lamp from operating, without setting this code. BCM cannot tell the difference between operating one or 2 relays.

Code B420, Flow Chart Twilight Relay Circuits (Optional On Riviera Only). Scheme 169

Code B420, Wiring Diagram Hi/Lo Beam Relay Circuit (Riviera Only). Scheme 170

If HI/LO beams did not cycle on and off when BO06 was selected, this is the system that set Code B420.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if fault is due to an open circuit or a short to ground in circuit. If "HI" beams are always on, there is a short to ground in control circuit. If "LO" beams are always on, there is an open in one of the circuits.
2. Checks to see if short to ground is due to circuit or BCM.
3. Checks to see if open circuit is due to circuit or BCM.
4. Checks to see if open circuit is on power or ground side of relay.

If an intermittent Code B420 is being set. Manipulate related wiring in output function and watch for relays to cycle. Since this code only monitors the control (winding) side of relays, it is possible for the relay to fail and/or circuits on relay contacts preventing "HI/LO" beam operation, without setting this code.

Code B420, Flow Chart Hi/Lo Beam Relay Circuit (Riviera Only). Scheme 171

Code B420, Wiring Diagram Hi/Lo Beam Relay Circuit (Reatta Only). Scheme 172

If HI/LO beams did not cycle on and off when BO06 was selected, this is the system that set Code B420.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if fault is due to an open circuit or a short to ground in circuit. If "HI" beams are always on, there is a short to ground in control circuit. If "LO" beams are always on, there is an open in one of the circuits.
2. Checks to see if short to ground is due to circuit or BCM.
3. Checks to see if open circuit is due to circuit or relay.
4. Checks to see if open circuit is on power or ground side of relay.
5. Checks to see if open circuit is in wiring or BCM

If an intermittent Code B420 is being set. Manipulate related wiring in output function and watch for relays to cycle. Since this code only monitors the control (winding) side of relays, it is possible for the relay to fail and/or circuits on relay contacts preventing "HI/LO" beam operation, without setting this code.

Code B420, Flow Chart Hi/Lo Beam Relay Circuit (Reatta Only). Scheme 173

Code B420, Wiring Diagram Retained Accessory Power Relay Circuit. Scheme 174

Whenever ignition is turned on, BCM will ground circuit No. 707, energizing both Retained Accessory Power (RAP) relays. This will provide power to power window and sunroof switches, radio, windshield wiper switch, trunk and glove box release switches, through circuit No. 660. If these functions do not work after RAP has been energized (by turning ignition on and off), with doors closed, or they remain working after door is opened, this is the system that set Code B420 (normal operation RAP time-out is 10 minutes). Circuit No. 70 is used as a backup to provide power to windows if there is a circuit fault (ignition has to be on). Circuit No. 41 is also used as a backup, but powers other functions when ignition is in accessory position since BCM is inactive and cannot ground circuit No. 707.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if fault is with RAP system or just a problem with one or more of the functions RAP provides power to.
2. Checks to see if fault is due to an open circuit or a short to ground in circuit. If the different functions always work, there is a short to ground in control circuit. If different functions do not work with RAP activated, there is an open in one of the circuits.
3. Checks to see if short to ground is due to circuit or BCM.
4. Checks to see if open circuit is due to circuit or BCM.
5. Checks to see if open circuit is on power or ground side of relay.

If an intermittent Code B420 is being set. Manipulate related wiring in output function and watch for relays to cycle. Since this code only monitors the control (winding) side of relays, it is possible for the relay to fail and/or circuits on relay contacts, preventing RAP operation, without setting this code. The BCM cannot tell the difference between operating one or 2 relays.

Code B420, Flow Chart Retained Accessory Power Relay Circuit. Scheme 175

Code B420, Wiring Diagram Courtesy - Twilight Light Relay Circuits (Toronado). Scheme 176

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

Note. Test numbers refer to numbers on diagnostic chart.

1. To determine which system has failed (courtesy lamps or twilight), select BCM output function in diagnostic mode. As the individual outputs cycle on and off, observe their actual operation.
2. Checks to see if short to ground is due to circuit or BCM.
3. Checks to see if open circuit is due to circuit or BCM.
4. Checks to see if open circuit is on power side of relay.
5. Checks to see if open circuit is on ground side of relay or in relay.

Code B420, Flow Chart Courtesy - Twilight Light Relay Circuits (Toronado). Scheme 177

Code B420, Wiring Diagram Twilight Light Relay Circuits (Toronado). Scheme 178

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

Note. Test numbers refer to numbers on diagnostic chart.

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

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

Code B420, Flow Chart Twilight Light Relay Circuits (Toronado). Scheme 179

Code B440, Wiring Diagram Air Mix Valve (Door) Circuit Problem. Scheme 180

Code B440 is set by BCM if commanded air mix door position is between 30 percent and 80 percent, but actual air mix door position is not within 2 percent of commanded position for 60 seconds. The BCM commands the programmer to move air mix valve (door) over data circuit No. 800. With ignition on, BCM supplies 5 volts on circuit No. 705 and ground on circuit No. 736. A motor in programmer drives air mix valve (door). The BCM monitors door position through a feedback pot on DC motor which varies between zero and 5 volts depending on air mix door position. If air mix valve (door) feedback indicates it is near hot or cold extreme, code will not set since mix door may be at its limit of travel and not able to reach commanded door position.

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

Note. Test numbers refer to numbers on diagnostic chart.

1. BD23 display indicates actual air mix valve (door) position. The normal range is between 1-99 percent. BCM override value BS01 display is for program number.
2. Checks to see if fault could be due to 5-volt reference and ground circuit, or sensor circuit.
3. Checks to see if fault is due to programmer or sensor circuit.
4. Checks to see if fault is due to circuit or BCM.
5. This step checks to see if open circuit reading is due to circuit No. 736 or circuit No. 705.

If an intermittent Code B440 is being set, check B440 snap data BD23 display. If it was zero percent, check for an intermittent open in circuit No. 736. If it was 100 percent, check for an intermittent open in circuit No. 733 or circuit No. 705. If it was 1-99 percent, check for binding door movement throughout range of door travel and check for a poor ground circuit No. 803. Manipulate related wiring while observing actual air mix door position (BD23 display) movement. If failure is induced, valve (door) position will either stop or jump to an extreme value (zero to 100 percent). This will assist in isolating location of malfunction. Exit diagnostics and select "Max Heat" (90°F) and "Max Cool" (60°F) using normal HVAC controls, waiting a minimum of 2 minutes in each mode to see if code sets.

Code B440, Flow Chart Air Mix Valve (Door) Circuit Problem. Scheme 181

Code B446, B447 & B448 Wiring Diagram (Reatta & Riviera) Refrigerant System Problem (1 OF 2). Scheme 182

Code B446, B447 & B448 Wiring Diagram (Toronado) Refrigerant System Problem (1 OF 2). Scheme 183

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

Note. Test numbers refer to numbers on diagnostic chart.

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

Code B446, B447 & B448 Flow Chart Refrigerant System Problem (1 OF 2). Scheme 184

Code B446, B447 & B448 Wiring Diagram (Reatta & Riviera) Refrigerant System Problem (2 Of 2). Scheme 185

Code B446, B447 & B448 Wiring Diagram (Toronado) Refrigerant System Problem (2 Of 2). Scheme 186

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

Note. Test numbers refer to numbers on diagnostic chart.

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

If codes B446 and B447 are both set, check low side temperature sensor and circuitry. If okay, evacuate and recharge system.

Code B446, B447 & B448 Flow Chart Refrigerant System Problem (2 Of 2). Scheme 187

Code B449, Wiring Diagram High Side Temperature Too High. Scheme 188

Code B449 is designed to disengage A/C compressor clutch in the event the high side refrigerant temperature exceeds 199°F (93°C). The A/C compressor clutch will reactivate once high side temperature falls to less than 199°F (93°C). Possible causes for excessively high A/C head pressures should be checked. Diagnose A/C system for refrigerant system performance.

CODE B450, COOLANT TEMPERATURE TOO HIGH

Code B450 is designed to disengage A/C compressor clutch if engine coolant temperature exceeds 261°F (126°C) and re-engage clutch when coolant temperature falls to less than 120°C. If Code EO14 is also stored, follow diagnosis for that code first. 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 coolant fan operation, faulty belt or tension, low coolant level and restrictions or faulty hoses and/or routings.

Code B482, Wiring Diagram Anti-Lock Pressure Problem. Scheme 189

This code indicates that brake pressure switch has indicated a low pressure condition to BCM. If Code B482 is set, and you are experiencing braking problems, diagnose ABS and normal braking system. Code B482 sets whenever circuit No. 933 is pulled low to ground and remains low for 50 seconds. As soon as circuit No. 933 goes low, the Red "Brake" telltale will illuminate. The warning message on the Digital Instrument Cluster (DIC) for "Low Brake Pressure" will not illuminate until after 50 seconds. The amber "Anti-Lock" telltale in the IPC is controlled only by ABS control unit.

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

Code B552, Wiring Diagram BCM Keep Alive Memory Error. Scheme 190

Code B552 does not necessarily indicate a fault, but is a normal occurrence anytime battery power or ground to 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, code will become "History" under the following conditions

1. Ignition in lock position.
2. Wait for 5 seconds.
3. Ignition key on, re-enter diagnosis.

After the above conditions have taken place, code should now be "History", and can be cleared in the normal manner. This code could be set if the system voltage drops to less than 8 volts at BCM terminal No. 1C9. Possible causes for this are faulty charging system, starter system, extreme cold weather and jump starting 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 during cranking mode.
3. Checks for adequate system voltage at BCM terminal No. 1C10. System voltage must not drop to less than 8 volts during engine cranking. By removing fuel pump fuse, engine will not start and voltage during engine cranking can be observed.

Code B552, Flow Chart BCM Keep Alive Memory Error. Scheme 191

Code C553, Wiring Diagram CRT Keep Alive Memory Error (Reatta & Riviera). Scheme 192

Code C553 does not necessarily indicate a fault, but is a normal occurrence anytime the power to CRTC has been interrupted. This code could set if the system voltage drops to less than 8 volts at CRT terminal "C1". Possible causes are faulty charging system, starter system, extreme cold weather or jump starting vehicle.

Diagnosis

With ignition key off, backprobe CRT controller terminals "C1" and "C8". Note voltage at key off and key on, during engine cranking and with engine running

1. If voltage remains greater than 8 volts at all times, check for poor terminal contact. If code persists, replace CRT controller.
2. If voltage remains less than 8 volts at all times, check for an open in circuit N. 801 and check for an open or short to ground on circuit No. 812.

Code C553, Flow Chart CRT Keep Alive Memory Error (Reatta & Riviera). Scheme 193

Code B556, Odometer (EE) Prom Error. Scheme 194

Code B556 indicates that EEPROM, which records elapsed odometer mileage, is not being read by BCM. Usually along with Code 556, "ERROR" will be displayed in the odometer display. The EEPROM contains specific vehicle information such as vehicle ID number, season odometer mileage and certain vehicle options. Since this information is programmed for the specific vehicle in which it is installed, a EEPROM cannot be transferred from one vehicle to another. Check for proper EEPROM installation. If the EEPROM is properly installed, no bent pins, but Code B556 persists, replace EEPROM. Replacement EEPROMs must be obtained through an authorized Delco Service Center.

Code B660, Wiring Diagram Cruise Control Not Drive. Scheme 195

Code B660 will set in the cruise control is engaged and BCM detects that gear selector is in Park, Reverse or Neutral. This is done by the BCM based on ECM's input for Park and Neutral, and through circuit No. 24 feeding directly to BCM for Reverse gear status ("HI" on circuit No. 24 indicates Reverse). During time failure is present, BCM will disengage cruise control.

Code B660, Flow Chart Cruise Control Not Drive. Scheme 196

Code B663, Wiring Diagram Cruise Speed Difference Between Actual And Set, Is Too Large. Scheme 197

Code B663 will set and disengage cruise control if actual speed is 30 MPH higher or lower than 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 operator accelerates, using accelerator pedal and drives 30 MPH greater than set speed. If operator experiences cruise drop out with this code set, but did not accelerate 30 MPH greater than set speed, a mechanical problem is indicated.

Note. Test numbers refer to numbers on diagnostic chart.

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

If Code B663 is setting intermittently, advise vehicle operator that overrunning the cruise control set speed by more than 30 MPH will cause this code to set. Check vacuum source and brake release vacuum lines for proper connections or slow leaks.

Code B663, Flow Chart Cruise Speed Difference Between Actual And Set, Is Too Large. Scheme 198

CODE B664, CRUISE - ACCELERATION TOO HIGH

This code will set and disengage the cruise control if vehicle acceleration exceeds a preset rate calibrated in the BCM. This could occur on slippery pavement or for some mechanical problems such as transmission slippage. Under these conditions, this code is normal. It should be cleared and vehicle operator should be advised of this.

Code B667, Wiring Diagram (1 of 2) Set/Coast Or Resume/Accel Circuit Shorted. Scheme 199

Code B667, Wiring Diagram (2 of 2) Set/Coast Or Resume/Accel Circuit Shorted. Scheme 200

When cruise control "ON/OFF" switch is turned "ON" and brake is released, system voltage is available at one side of normally open contacts on "SET/COAST" and "RESUME/ACCEL" switches. If "SET/COAST" or "RESUME/ACCEL" switches were stuck, or their signal wires to BCM were shorted to voltage, vehicle could begin cruise operation. In order to prevent this occurrence, Code B667 will set and disable cruise control, if signal voltage from "SET/COAST" circuit No. 84 or "RESUME/ACCEL" circuit No. 87, is high when cruise control "ON/OFF" switch is turned from "OFF" to "ON" or when ignition key is turned on and cruise control "ON/OFF" switch was left "ON". Cruise control will be disabled until BCM sees a low on both of these signals.

Note. Test numbers refer to numbers on diagnostic chart.

1. BI76 and BI77 will display "SET/COAST" and "RESUME/ACCEL" switch status as "HI" or "LO", depending on voltage state at BCM. If one of these inputs stays "HI" when switches are cycled, that particular switch or signal wire is shorted to voltage.
2. This step checks to see if short circuit reading is due to switch or circuit.
3. This step checks to see if vacuum leak is due to vacuum source or servo.
4. This step checks to see if fault is due to intermittent or slow vacuum leak.
5. This step checks to see if fault is servo or brake vacuum release circuit.

If Code B663 is setting intermittently, advise vehicle operator that "overruning" the cruise control set speed by more than 30 MPH will cause this code to set. Check vacuum source and brake release vacuum lines for proper connections or slow leaks.

Code B667, Flow Chart Set/Coast Or Resume/Accel Circuit Shorted. Scheme 201

Code B671, Wiring Diagram (Reatta & Riviera) Cruise Servo Position Sensor Circuit. Scheme 202

Code B671, Wiring Diagram (Toronado) Cruise Servo Position Sensor Circuit. Scheme 203

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

Note. Test numbers refer to numbers on diagnostic chart.

1. BD70 display indicates servo position. Normal range is greater than 3 percent.
2. Check to see if fault is due to short or open in feedback circuits. Normal resistance across feedback coil should be 15-30 ohms.
3. Checks to see if open circuit is due to servo or circuits.
4. Checks to see if problem is intermittent. BD70 display will not go as low or high as BS05 display, because of its mechanical limits of travel. It should never go to less than 3 percent.

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

Code B671, Flow Chart Cruise Servo Position Sensor Circuit. Scheme 204

Code B672, Wiring Diagram (Reatta & Riviera) Cruise Vent Solenoid Circuit Problem. Scheme 205

Code B672, Wiring Diagram (Toronado) Cruise Vent Solenoid Circuit Problem. Scheme 206

The cruise control vent solenoid receives pulsed voltage signals from BCM to control the amount of time solenoid is energized. While time output is "HI", solenoid is energized and vacuum is not vented (or it is trapped) in servo. Code B672 will set if cruise is "ON", brake is not depressed and BCM output is "HI". Under either of these conditions, BCM will disable cruise control until it sees proper output signals. These determinations are made internal to BCM and may, or may not, affect "HI" or "LO" reading displayed during service mode. An output display of "LO" indicates circuit No. 403 should be de-energized (vent solenoid off) and an output display of "HI" indicates circuit No. 403 should be energized (vent solenoid on).

Circuit No. 403 will be "HI" when solenoid is energized as BCM is providing voltage to vent solenoid which has its own full time ground. Circuit No. 403 will be "LO" when the solenoid is de-energized as BCM removes voltage feed to solenoid.

Note. Test numbers refer to numbers on diagnostic chart.

1. BO01 cycles vent solenoid. The "HI" and "LO" refer to commanded state of voltage at 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 related wiring while in BO01 display and listen for 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. Ensure intermittent condition can be induced a few times during the on (or "HI") output interval.

Code B672, Flow Chart Cruise Vent Solenoid Circuit Problem. Scheme 207

Code B673, Wiring Diagram (Reatta & Riviera) Cruise Vacuum Solenoid Circuit Problem. Scheme 208

Code B673, Wiring Diagram (Toronado) Cruise Vacuum Solenoid Circuit Problem. Scheme 209

The cruise control vent solenoid receives pulsed voltage signals from BCM to control the amount of time solenoid is energized. While time output is "HI", solenoid is energized and vacuum is not vented (or it is trapped) in servo. Code B673 will set if cruise is "ON", brake is not depressed and BCM output is "HI". Under either of these conditions, BCM will disable cruise control until BCM sees proper output signals. These determinations are made internal to BCM and may or may not affect "HI" or "LO" reading displayed during service mode. An output display of "LO" indicates circuit No. 403 should be de-energized (vent solenoid off) and an output display of "HI" indicates circuit No. 402 should be energized (vent solenoid on). Circuit No. 402 will be "HI" when solenoid is energized as BCM is providing voltage to vent solenoid which has its own full time ground. Circuit No. 402 will be "LO" when the solenoid is de-energized as the BCM removes voltage feed to solenoid.

Note. Test numbers refer to numbers on diagnostic chart.

1. BO02 cycles vacuum solenoid. The "HI" and "LO" refer to commanded state of voltage at 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 vacuum solenoid is shorted (less than 25 ohms) BCM replacement will also be necessary.

If an intermittent Code B673 is being set, manipulate related wiring while in BO02 display and listen for 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. Be aware that solenoid could be at end of 3 second interval. Ensure intermittent condition can be induced a few times during the on (or "HI") output interval.

Code B673, Flow Chart Cruise Vacuum Solenoid Circuit Problem. Scheme 210

CODE C553, CRT KEEP ALIVE MEMORY ERROR (TORONADO)

Code C553 does not necessarily indicate a fault, but is a normal occurrence anytime power to the CRTC has been interrupted. This code could set if the system voltage drops to less than 8 volts at CRT terminal "A7". Possible causes for this are the following

1. Faulty charging system.
2. Faulty starter system.
3. Extreme cold weather.
4. Jump starting vehicle.

CODE C710, CRTC SWITCHING CIRCUIT PROBLEM (REATTA & RIVIERA)

This code indicates there is an intermittent problem with CRT's switching circuits. If fault was present, you would not be able to enter diagnostics to see this code. If this code is set, there is an intermittent problem within the 4 data circuits, the keyboard feedback circuit, or the 5-volt power or ground circuit. Manipulate these circuits while checking continuity, or by using Tester J-34914. Since intermittent problem is the switches not responding, continually select different switches while manipulating circuits. When failure occurs, switches on circuit will not work.

Code C710 will only show up as a "History" code, as it indicates a problem in switches. If problem was "Current", you would not be able to enter diagnostics to see code. If Code C710 "History" appears, this indicates an intermittent open in circuits No. 220, 221, 222, 223, 836 or an intermittent open, or short to ground in circuits No. 332 or 305. Failure condition must be present for 9 seconds to set this code.

Code C710, Wiring Diagram (Reatta & Riviera) CRTC Switching Circuit Problem. Scheme 211

Code C710, Wiring Diagram (Toronado) CRTC Switching Circuit Problem. Scheme 212

Note. Test numbers refer to numbers on diagnostic chart.

1. CRT monitor needs communication from the CRTC to initially illuminate. Therefore, if CRT monitor lights initially it is receiving signals from CRTC.
2. If CRT is blank at times and Code C710 is set, monitor is not receiving data intermittently.
3. Checks voltage on CRTC to CRT data line, normal voltage is between 1.5 and 4.5 volts and fluctuates some.
4. Checks whether CRT or CRTC are causing low voltage reading on data line.

Check connections at CRT monitor and controller. If both connections are clean and tight, either CRT monitor or controller could be at fault.

Code C710, Flow Chart CRTC Switching Circuit Problem. Scheme 213

"Driver Door Ajar" Message - Wiring Diagram. Scheme 214

BCM supplies and monitors voltage on circuit No. 3C12. If voltage is sensed as being low (door ajar), BCM will display "Driver Door Ajar" message under the following conditions

1. PRNDDL is okay.
2. Engine is running.
3. Transmission not in Park or Neutral.
4. Driver door ajar switch input is low.

Or if the following conditions exist

1. "Driver Door Ajar" failure code already set.
2. Driver door ajar switch is closed.

If system is to be tested, ensure that Code B334 is not set (ECM UART data line is okay).

"Passenger Door Ajar" Message - Wiring Diagram. Scheme 215

BCM supplies and monitors voltage on circuit No. 3C14. If voltage is sensed as being low (door ajar), BCM will display "Driver Door Ajar" message under the following conditions

1. PRNDDL is okay.
2. Engine is running.
3. Transmission not in Park or Neutral.
4. Driver door ajar switch input is low.

Or if the following conditions exist

1. "Driver Door Ajar" message already set.
2. Driver door ajar switch is closed.

If system is to be tested, ensure that Code B334 is not set (ECM UART data line is okay).

"Seat Belt" Telltale & Chime - Wiring Diagram. Scheme 216

BCM supplies and monitors voltage on circuit No. 3C15. If voltage is sensed as being low (seat belt unbuckled), BCM will display "Seat Belt" message under the following conditions

1. Engine is running.
2. Seat belt unbuckled.
3. Engine running time less than 6 seconds.

"Headlights Are On" Chime - Wiring Diagram. Scheme 217

BCM monitors terminal No. 2B7. When parking light switch is closed, voltage is sensed by BCM through circuit No. 308. When parking light switch is open, zero voltage will be sensed by the BCM. BCM will display "Headlamps Are On" message under the following conditions

1. Parking light switch is on.
2. Key not in ignition.
3. Driver door is open.
4. Ignition is off.

"Low Oil Pressure" Message & Telltale - Wiring Diagram. Scheme 218

Oil pressure sensor is a variable resistor the changes resistance proportional to oil pressure. BCM monitors resistance at terminal No. 3D9. If oil pressure drops to less than 6 psi, BCM will illuminate "Low Oil Pressure" message. This will occur after engine has been running for at least 5 seconds and if the following conditions exist

1. Oil pressure is less than 6 psi.
2. Engine speed greater than 600 RPM.
3. Above failure conditions present for a predetermined time.

Or if the following conditions exist

1. Code B334 is set.
2. Oil pressure is less than 6 psi.

"Oil Level Is Low" Message - Wiring Diagram. Scheme 219

The BCM supplies and monitors voltage at terminal No. 1D1. When oil level switch is closed (normal oil level), BCM will sense low voltage. If oil level switch is open (low oil level), BCM will sense high voltage and illuminate "Oil Level Is Low" message. This will occur under the following conditions

1. No Code B334.
2. Coolant sensor operating properly.
3. Coolant temperature drop since last ignition cycle, greater than predetermined degrees.

"Fuel Level Is Low" Message - Wiring Diagram. Scheme 220

The BCM monitors the fuel level sender in the fuel tank at terminal No. 2B8. If the average calculated fuel is 1.9 gallons or less, the "Fuel Level Is Low" (or lowest bar of fuel gauge will flash) message will be illuminated.

"Washer Fluid Is Low" Message - Wiring Diagram. Scheme 221

The BCM supplies and monitors voltage at terminal No. 2A4. When fluid level circuit is open, BCM will sense high voltage. When fluid level circuit is closed (low washer fluid), BCM will sense low voltage and illuminate "Washer Fluid Is Low" message. BCM will illuminate message if low washer fluid exist for at least 15 seconds.

"Overspeed Alarm" Message - Wiring Diagram. Scheme 222

The overspeed alarm is an operator-control vehicle speed warning designed to alert driver that vehicle speed has exceeded set point. The "Overspeed Alarm" message will appear when vehicle speeds set point and disappear if overspeed alarm is reset or vehicle speed drops to less than set point. Diagnosis of vehicle speed sensor may be required. BCM will display message if the following conditions exist

1. Code B124 not set current.
2. Overspeed set point not zero MPH.
3. Vehicle speed greater than overspeed set point.

"Key In Ignition" Warning Chime - Wiring Diagram. Scheme 223

The BCM supplies and monitors voltage at terminal No. 3C13. When ignition switch circuit is closed (ignition key in lock position) voltage is pulled low, BCM will display "Key In Ignition" message under the following conditions

1. Key in ignition.
2. Driver door is open.
3. Ignition is off.

Flashing Coolant Gauge, - Wiring Diagram "Hot" Telltale,"Engine Overheat" Message & Fast Chime. Scheme 224

The ECM supplies and monitors voltage from coolant temperature sensor circuit at terminal No. 3D4. BCM will check the ECM (through UART data line circuit No. 800) every one second. If the calculated coolant temperature reaches 126°C and other failure conditions are met, BCM will display message. The following are failure conditions that BCM must see to display message

1. Engine coolant temperature greater than 126°C.

Or the following conditions.

1. Engine overheat condition already present.
2. Engine coolant temperature greater than 120°C.

Diagnosis of coolant temperature sensor and/or circuit may be necessary.

"Park Brake On" Message - Wiring Diagram. Scheme 225

The BCM supplies and monitors voltage from parking brake switch at terminal No. 1C5. When parking brake is pulled, switch is closed (grounded). BCM senses voltage being pulled low and illuminates "Park Brake On" message. BCM will display message under the following failure conditions

1. Park brake is applied (switch is closed).
2. Ignition is on.
3. Transmission not in Park or Neutral.

"Brake Fluid Is Low" Message - Wiring Diagram. Scheme 226

The BCM supplies and monitors voltage from brake fluid level switch at terminal No. 1C2. When brake fluid level is low (switch closed), BCM senses voltage being pulled low, and will illuminate "Brake Fluid Is Low" message if condition exists for at least 5 seconds. On vehicles without ABS, a brake fluid pressure switch is also used and functions the same as brake fluid level switch.

Antilock Telltale On - Wiring Diagram. Scheme 227

If this telltale is activated check brake fluid level. If brake fluid level is okay, ABS system requires diagnosis. For complete diagnosis and testing, see appropriate ABS article in BRAKES section.

Scheme 228

Riviera BCM Wiring Diagram. Scheme 229

Toronado Wiring Diagram. Scheme 230