Body Control Module Cadillac Eldorado X

DESCRIPTION & OPERATION

Note. Body Control Module (BCM) may be referred to as Platform Zone Module (PZM).

The Body Control Module (BCM) performs the following functions: HVAC afterblow control, battery guard, door lock and unlock, fuel level for DIC, retained accessory power, theft deterrent, exterior and interior lighting control, trunk release, time of day for radio display, rear defog, fuel door release, and vehicle personalization.

Signals that activate the BCM are known as "wake-up" signals. BCM is asleep when it is not controlling or monitoring the following wake-up functions: Key in door lock switch, door ajar switches, power door lock switches, trunk ajar switch, trunk tamper switch, ignition on, ignition accessory (ACC), and any class 2 communication requiring PZM interaction.

BCM uses class 2 serial data line to communicate with other system control modules. Class 2 serial data is transmitted on a single wire at an average of 10.4 Kbps (10,400 bits per second). Class 2 uses a variable pulse width modulation to carry data, and speed is determined by message being transmitted. The bus is active at 7 volts nominal and inactive at ground potential. Class 2 serial data line is tolerant to different levels of ground potential.

SELF-DIAGNOSTIC SYSTEM

Note. Vehicles with analog instrument panel cluster are equipped with a Climate Control Panel (CCP). Vehicles with digital instrument panel cluster are equipped with a Climate Control Center (CCC). References to CCP also include CCC.

Body Control Module (BCM) is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, BCM will store a 5-digit alphanumeric code.

After BCM trouble codes have been displayed, service mode can be used to clear codes and exit diagnostics or individually perform other tests on different systems. To continue with system diagnostics, see SERVICE MODE OPERATION. To exit diagnostic mode, press DEFOG or MODE button on CCP, or turn ignition off. Codes will not be cleared. System will return to normal vehicle operation.

ENTERING & EXITING DIAGNOSTICS

Note. If vehicle is to be operated in diagnostics without engine running for an extended time period, use battery charger to prevent battery from running down or system setting false diagnostic information.

Climate Control Panel (CCP) is used to display Body Control Module (BCM) information while in diagnostic mode. CCP displays Diagnostic Trouble Codes (DTCs) for Powertrain Control Module (PCM), Instrument Panel Cluster (IPC), Air Control Module (ACM), Supplemental Inflatable Restraint (SIR), Traction Control System (TCS), Road Sens-ing Suspension (RSS), Body Control Module (BCM), Integrated Radio Controller (IRC), Remote Function Actuator (RFA), Climate Control Panel (CCP), and Cellular Telephone (PHN).

1. To enter diagnostic mode, turn ignition on. Simultaneously press OFF and WARMER (red bar) buttons on climate control center (digital instrument panel), or OFF and PASSENGER WARMER on climate control panel (analog instrument panel). Continue pressing appropriate buttons until segment check appears (about 3 seconds) on Instrument Panel Control (IPC). NOTE: Failure of any segment to glow may result in inaccurate test results (turn signal indicators should not be lit). Replace any inoperative segment display before proceeding with self-diagnostic process.
2. When segment check appears (all segments glow), system has entered diagnostic mode. Release both buttons. Driver Information Center (DIC) portion of IPC will display Diagnostic Trouble Codes (DTCs). Diagnostic trouble codes will be displayed in levels beginning with PCM codes first, followed by IPC, ACM, SIR, TCS, RSS, PZM codes, etc. (if so prompted).
3. To select PZM level, press and release CCP LO (fan down) button until PZM level is displayed. After codes are displayed, press CCP HI (fan up) button to enter service mode or press OFF button to return to next selection in previous test level. To continue with system diagnostics, see «SERVICE MODE OPERATION»(/cadillac/eldorado/x-1992-2002/remont/body-cab-control-systems/#body-control-module__service-mode-operation) .
4. To exit diagnostic mode, press DEFOG or MODE button on CCP, or turn ignition off. Codes will not be cleared. System will return to normal vehicle operation.

STATUS LIGHTS DISPLAY

Upon entering PZM level of diagnostic mode, indicator lights on Climate Control Panel (CCP) are used to indicate status of certain inputs and operating modes. Operational status of these components is indicated by corresponding status light being on or off. (Scheme 1)and (Scheme 2).

Scheme 1

Scheme 2

SERVICE MODE OPERATION

Note. PCM, IPC, ACM, SIR, TCS, RSS, IRC, RFA, CCP and PHN systems can also be tested in service mode. Only information related to PZM diagnosis is covered in this article.

After PZM trouble codes have been displayed, service mode can be used to clear codes and exit diagnostics or individually perform other tests on different systems.

Selecting System Level

Following trouble code display, first available system will be displayed (i.e., PCM?, IPC?, ACM?, etc.). When selecting a system to test, any of the following actions may be taken to control display

1. Pressing LO (fan down) button on CCP will display next available system selection (i.e., SIR?, TCS?, RSS?, PZM?, etc.). This allows display to be cycled through all system choices. List of systems can be repeated following end of system list.
2. Pressing HI (fan up) button on CCP will select displayed system for testing (i.e., PZM DATA, PZM INPUTS, PZM OUTPUTS, etc.). (Scheme 3)
3. Pressing OFF button on CCP will stop system selection process and return display to beginning of PZM trouble code sequence.

Selecting Test Type Level

Selection of "DATA?", "INPUTS?", "OUTPUTS?", "OVERRIDES?", "CLEAR CODES?" or "SNAPSHOT?" test type may be displayed. (Scheme 3) If dashes appear in DIC, test is not valid or test conditions are wrong. While selecting a specific test, any of following actions may be taken to control display

1. Pressing HI (fan up) button on CCP will display a specific output or test parameter for selected test type level (i.e., PZM data parameter PZ D01, etc.). (Scheme 3)
2. Pressing LO (fan down) button on CCP will display next test type level for system level (i.e., PZM INPUTS?, PZM OUTPUTS?, etc.). (Scheme 3) This allows display to be cycled through all available test type choices. List of test types can be repeated following display of last test type.
3. Pressing OFF button on CCP will stop test selection process and return display to next system level (i.e., IRC?, etc.).

Selecting Clear Codes

Selecting "CLEAR CODES?" test will result in "CODES CLEAR" message being displayed with selected system name for 3 seconds, indicating all stored trouble codes have been erased from memory. After 3 seconds, display will automatically return to next available test type level (i.e., PZM SNAPSHOT?, etc.).

After a code has been cleared, make a complete ignition cycle and possibly a test drive. Ensure code does not reset.

Scheme 3

PZM DATA CODES

PZM data selection provides display of actual analog value as indicated by system.

PZM INPUT CODES

PZM input selection provides testing of inputs to PZM. Input status is shown on display as HI or LO. Input test status is shown as "0" until PZM sees a transition in state of switch; status then changes from "0" to "X", indicating test has been passed.

PZM OUTPUT CODES

Note. All PZM output tests are to be performed with key on, engine off.

PZM output selection provides ability to cycle PZM-controlled outputs. DIC display identifies solenoid or relay and state PZM is commanding that device. HI indicates solenoid or relay is de-energized and LO indicates solenoid or relay is energized.

PZM OVERRIDE CODES

PZM override selection provides testing of certain system functions regardless of normal program instructions, as long as test conditions are met. When a test is selected, current mode of function will be displayed as a percentage on Driver Information Center (DIC). If test conditions are not met, DIC will display "==" instead of override value selected.

DIC display will alternate between "--" and normal programmed command. Pressing WARMER button will increase override value and pressing COOLER button will decrease override value. Upon release of button, display may either remain at overridden value or automatically return to normal program control, depending on which function is being overridden. Selection of another override test will cancel current override.

BCM DTC DEFINITION

BCM COMMUNICATION PROBLEMS

BCM DTC DEFINITION

BCM LOCATION

BCM is located in trunk, on electronic module center, attached to back of rear seat.

DIAGNOSIS & REPAIR

Note. Body Control Module (BCM) may be referred to as Platform Zone Module (PZM).

Note. For wiring and connector terminal identification, see WIRING DIAGRAM .

Note. Use adapter from Terminal Test Adapter Kit (J 35616-A) connected to DVOM when making all measurements.

CLASS 2 SERIAL DATA LINE SYSTEM CHECK

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

Testing

1. Turn ignition switch to ON position. Connect scan tool. Attempt to establish communications with PZM. If communication cannot be established, go to next step. If communication can be established, record any DTCs that may be present. See appropriate «TESTS W/CODES»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l) article in ENGINE PERFORMANCE section.
2. Using scan tool, attempt to establish communications with another system on Class 2 serial data line. If communication cannot be established, go to CHART A, SCAN TOOL WILL NOT COMMUNICATE. If communication can be established, check for poor connection at PZM 24-pin connector C1 terminals B3 (Orange wire) and A12 (Black wire). If circuits are okay, replace PZM.

CHART A, SCAN TOOL WILL NOT COMMUNICATE

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

1. Enter on-board diagnostics. If on-board diagnostics can be entered, go to next step. If on-board diagnostics cannot be entered, go to step 3).
2. Turn ignition switch to OFF position. Disconnect PZM connector. Using DVOM, check resistance between Data Link Connector (DLC) terminal No. 2 (Purple wire) and PZM 24-pin connector C1 terminal B9 (Purple wire). If resistance is 5 ohms or less, scan tool may be malfunctioning. See scan tool manufacturer's instructions. If resistance is greater than 5 ohms, repair open in Purple wire.
3. Turn ignition switch to OFF position. Disconnect all modules connected to Class 2 serial data line. Using DVOM, check resistance between DLC terminal No. 2 (Purple wire) and ground. If resistance is infinite, go to next step. If resistance is not infinite, repair short to ground in Purple wire.
4. Turn ignition switch to ON position. Using DVOM, check voltage between DLC terminal No. 2 (Purple wire) and ground. If no voltage exists, go to next step. If any voltage exists, repair short to voltage in Purple wire.
5. Turn ignition switch to OFF position. Ensure Instrument Panel Cluster (IPC) is connected. Using scan tool, attempt to establish communications with IPC. If communication can be established, go to next step. If communication cannot be established, replace IPC. See appropriate «INSTRUMENT PANEL»(/cadillac/eldorado/x-1992-2002/remont/gauges-instrument-panels/#instrument-panel) article.
6. Ensure ignition switch is in OFF position. In the following order, individually reconnect each module (if equipped): Body Control Module (PZM) Remote Function Actuator (RFA) Instrument Panel Cluster (IPC) Sensing & Diagnostic Module (SDM) Electronic Brake Traction Control Module (EBTCM) Powertrain Control Module (PCM) Heater & A/C Programmer (ACM) Amplifier Electronic Suspension Module Radio (IRC) Memory Seat Module (MSM) Cellular Phone Module (PHN) Memory Mirror Module (MMM) Climate Control Panel (CCP)

Using scan tool, attempt to establish communication with reconnected module. When communication cannot be established, replace most recently connected module.

DTC U1016, LOSS OF SERIAL COMMUNICATIONS - PCM

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

Every 2 seconds while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to indicate system is operating properly. Signal is then transmitted to PZM. DTC U1016 will set when PZM does not receive signal from Powertrain Control Module (PCM) after 3 consecutive monitoring cycles. DTC U1016 will clear when PCM transmits signal to PZM.

1. If multiple class 2 codes are set as current (i.e., U1300, U1301, U1088 or U1153), check for an intermittent short to ground or battery in Purple wire between individual control modules.
2. If DTC is current, attempt to establish communications with PCM using scan tool. If communication cannot be established, diagnose PCM. See appropriate TESTS W/CODES article in ENGINE PERFORMANCE section. If communication can be established, replace PZM.
3. If DTC is history, check for intermittent open in Purple wire between individual control modules.

DTC U1088, LOSS OF SERIAL COMMUNICATIONS - SIR

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

Every 2 seconds while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to indicate system is operating properly. Signal is then transmitted to PZM. DTC U1088 will set when PZM does not receive signal from Sensing and Diagnostic Module (SDM) after 3 consecutive monitoring cycles. DTC U1088 will clear when SDM transmits signal to PZM.

1. If multiple class 2 codes are set as current (i.e., U1300, U1301, U1088 or U1153), check for an intermittent short to ground or battery in Purple wire between individual control modules.
2. If DTC is current, attempt to establish communications with SDM using scan tool. If communication cannot be established, diagnose problem and repair in air bag system. See appropriate AIR BAG RESTRAINT SYSTEM article. If communication can be established, replace PZM.
3. If DTC is history, check for intermittent open in Purple wire between SDM and individual control modules.

DTC U1096, LOSS OF SERIAL COMMUNICATIONS - IPC

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

Every 2 seconds while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to indicate system is operating properly. Signal is then transmitted to PZM. DTC U1096 will set when PZM does not receive signal from Instrument Panel Cluster (IPC) after 3 consecutive monitoring cycles. DTC U1096 will clear when IPC transmits signal to PZM.

1. If multiple class 2 codes are set as current (i.e., U1300, U1301, U1088 or U1153), check for an intermittent short to ground or battery in Purple wire between individual control modules.
2. If DTC is current, attempt to establish communications with IPC using scan tool. If communication cannot be established, diagnose and repair problem in instrument cluster. See appropriate «INSTRUMENT PANEL»(/cadillac/eldorado/x-1992-2002/remont/gauges-instrument-panels/#instrument-panel) article. If communication can be established, replace PZM.
3. If DTC is history, check for intermittent open in Purple wire between IPC and individual control modules.

DTC U1153, LOSS OF SERIAL COMMUNICATIONS - CCP

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

Every 2 seconds while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to indicate system is operating properly. Signal is then transmitted to PZM. DTC U1153 will set when PZM does not receive signal from Climate Control Panel (CCP) after 3 consecutive monitoring cycles. DTC U1153 will clear when CCP transmits signal to PZM.

1. If multiple class 2 codes are set as current (i.e., U1300, U1301, U1088 or U1153), check for an intermittent short to ground or battery in Purple wire between individual control modules.
2. If DTC is current, attempt to establish communications with CCP using scan tool. If communication cannot be established, diagnose and repair problem in A/C system. See «A/C SYSTEM GENERAL SERVICING»(/cadillac/eldorado/x-1992-2002/remont/general-servicing-all-makes/#hvac-system-general-servicing) article in AIR CONDITIONING & HEAT section. If communication can be established, replace PZM.
3. If DTC is history, check for intermittent open in Purple wire between CCP and individual control modules.

DTC U1169, LOSS OF SERIAL COMMUNICATIONS - MMM

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

Every 2 seconds while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to indicate system is operating properly. Signal is then transmitted to PZM. DTC U1169 will set when PZM does not receive signal from Memory Mirror Module (MMM) after 3 consecutive monitoring cycles. DTC U1169 will clear when MMM transmits signal to PZM.

1. If multiple class 2 codes are set as current (i.e., U1300, U1301, U1088 or U1153), check for an intermittent short to ground or battery in Purple wire between individual control modules.
2. If DTC is current, attempt to establish communications with MMM using scan tool. If communication cannot be established, diagnose and repair problem with memory mirror. See appropriate POWER SEATS article. If communication can be established, replace PZM.
3. If DTC is history, check for intermittent open in Purple wire between MMM and individual control modules.

DTC U1255, CLASS 2 INITIALIZATION ERROR

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

When vehicle is started, PZM requests information from other modules on Class 2 serial data line. DTC U1255 will set when PZM request information from a particular module, and that module is not "on-line". PZM will then use default values. DTC U1255 will clear when module providing the requested informations comes back "on-line".

1. Clear DTCs and cycle ignition. Check for DTCs. If DTC U1255 exists, use scan tool to establish communications with each module on Class 2 data bus. Repair or replace as necessary.
2. Check for intermittent open in Purple wire between individual control modules. If circuit is okay, replace PZM.

DTC U1300, CLASS 2 SHORT TO GROUND

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

When PZM is energized, it monitors Class 2 serial data line for a short to ground. DTC U1300 will set when PZM determines Class 2 serial data line is shorted to ground for 10 seconds or more. PZM will then use default values. DTC U1300 will clear when PZM determines Class 2 serial data line is no longer shorted to ground.

DTC U1300 should always be a history code. If DTC U1300 is current, modules on Class 2 serial data line cannot communicate with each other or diagnostic equipment. Check for intermittent short to ground in Purple wire between individual control modules.

DTC U1301, CLASS 2 SHORT TO VOLTAGE

Note. To identify wire colors and components on Class 2 serial data line, see appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.

When PZM is energized, it monitors Class 2 serial data line for a short to voltage. DTC U1301 will set when PZM determines Class 2 serial data line is shorted to voltage for 10 seconds or more. PZM will then use default values. DTC U1301 will clear when PZM determines Class 2 serial data line is no longer shorted to voltage.

DTC U1301 should always be a history code. If DTC U1301 is current, modules on Class 2 serial data line cannot communicate with each other or diagnostic equipment. Check for intermittent short to voltage in Purple wire between individual control modules.

DTC B0532, FUEL LEVEL SENDER SHORT TO GROUND

PZM monitors fuel level, and transmits this information over Class 2 serial data line to Powertrain Control Module (PCM) and Instrument Panel Cluster (IPC). When ignition switch is in RUN position, PZM continually measures voltage at 24-pin connector C1 terminal A1 (Purple wire) and determines position of sender by calculating percentage of IGN-1 present at terminal.

DTC B0532 will set if percentage of IGN-1 voltage is less than an acceptable level for at least 2 seconds. PZM will send a Class 2 message to PCM that percentage of IGN-1 is too low. DTC B0532 will clear if percentage of IGN-1 voltage meets or exceeds an acceptable level for at least one cycle.

1. If DTC B1982 or B1983 is current, DTC B0532 will not be set, but a Class 2 message will be sent to PCM that percentage of IGN-1 is too low. Check for short to ground in Purple wire between PZM and fuel level sender. Repair as necessary. If circuit is okay, go to next step.
2. If DTC B0532 is current, replace PZM. If DTC B0532 is history, replace fuel level sender.

DTC B0533, FUEL LEVEL SENDER SHORT TO VOLTAGE

PZM monitors fuel level, and transmits this information over Class 2 serial data line to Powertrain Control Module (PCM) and Instrument Panel Cluster (IPC). When ignition switch is in RUN position, PZM continually measures voltage at 24-pin connector C1 terminal A1 (Purple wire) and determines position of sender by calculating percentage of IGN-1 present at terminal.

DTC B0533 will set if percentage of IGN-1 voltage is greater than an acceptable level for at least 2 seconds. PZM will send a Class 2 message to PCM that percentage of IGN-1 is too high. DTC B0533 will clear if percentage of IGN-1 voltage is less than or equal to an acceptable level for at least one cycle.

1. If DTC B1982 or B1983 is current, DTC B0533 will not be set, but a Class 2 message will be sent to PCM that percentage of IGN-1 is too high. Check for short to voltage in Purple wire between PZM and fuel level sender. Repair as necessary. If circuit is okay, go to next step.
2. If DTC B0533 is current, replace PZM. If DTC B0533 is history, replace fuel level sender.

DTC B1552, LOSS OF PZM KEEP ALIVE MEMORY (KAM)

DTC B1552 indicates keep alive memory or long term memory has been reset. Keep alive memory or long term memory will reset when power or ground is removed from PZM. This is a normal occurrence when battery is disconnected and reconnected. When DTC B1552 is set, PZM memory is reset to initial values. PZM will initialize keep alive memory contents to default the following

1. Fuel Level - Empty
2. Afterblow Mode - Disable
3. Afterblow Alarm - Disable
4. Controlled Power Timer - Set To Full Time
5. Power Down Hours - Clear
6. Storage Mode State - Disable
7. Key Cylinder State - Inactive
8. Driver Door Jamb - Closed
9. Other Doors Jamb - Closed
10. Ignition State - Current State

If DTC B1552 is set and battery was not disconnected, check for poor connections at PZM 24-pin connector C1 terminals B3 (Orange wire) and A12 (Black wire).

DTC B1556, PZM EEPROM WRITE ERROR

DTC B1556 testing is run for each write block of writes to EEPROM. PZM writes to EEPROM cell and then reads data back. DTC B1556 will set when data read by PZM does not match data written to EEPROM after 2 consecutive attempts. DTC B1556 will clear when data read by PZM matches data written to EEPROM. If DTC B1556 is set, clear DTCs and cycle ignition. If DTC B1556 sets, replace PZM.

DTC B1558, PZM EEPROM CHECKSUM ERROR

Within 2.5 seconds after ignition switch is turned to RUN position, PZM adds the checksum of EEPROM block. DTC B1558 will set when value of addition does not equal zero. When DTC B1558 is set, PZM will clear all codes, set DTC B1558 as current and default to the following

1. Personalization - Factory Default
2. Ignition Cycle Counter - Zero
3. Theft Alarm Condition - Cleared

If DTC B1558 is set, clear DTCs and cycle ignition. If DTC B1558 sets, replace PZM.

DTC B1970, EXTERIOR LIGHT POWER FAULT

PZM commands exterior lights on by energizing headlight and parking light relays. DTC B1970 will set when exterior lights have been commanded on, but PZM does not sense exterior light power on after 2 consecutive monitoring cycles. When DTC B1970 is set, PZM will command exterior lights off, then attempt to turn exterior lights on until lights are no longer required. DTC B1970 will clear when exterior lights are commanded on and PZM senses exterior light power on after 2 consecutive monitoring cycles.

1. Turn ignition switch to OFF position. Remove parking light relay and headlight relay. Disconnect PZM connectors. Using DVOM, check resistance between parking light relay connector terminal A6 (White wire) and ground. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, replace PZM.
2. Repair short to ground in White wire between parking light relay and PZM. Reconnect all components. Turn ignition switch to ON position. Turn headlights on. If headlights do not come on, replace PZM. If headlights come on, system is functioning normally.

DTC B1971, INADVERTENT POWER FAULT

When PZM grounds inadvertent power relay, inadvertent power is commanded on and off. Battery voltage is supplied to components powered by inadvertent power relay when relay is energized. DTC B1971 will set when inadvertent power relay is commanded on or off and PZM feedback state does not match commanded state for at least 2 seconds. When DTC B1971 is set, PZM will continue to command requested state of relay until it is achieved or no longer necessary. DTC B1971 will clear when PZM feedback state matches commanded state for at least 2 seconds.

1. Turn ignition switch to OFF position. Connect scan tool and select BCM TEST. Select INADV. POWER. Turn inadvertent power on. Turn interior lights on. If interior lights illuminate, go to step 4). If interior lights do not illuminate, go to next step.
2. Remove inadvertent power relay. Using DVOM, check voltage between inadvertent power relay terminal A1 (Orange wire) and ground. If battery voltage exists, go to next step. If battery power does not exist, repair open or short to ground in Orange wire between inadvertent power relay and engine compartment fuse/relay center.
3. Using scan tool, turn inadvertent power on. Using DVOM, check resistance between inadvertent power relay terminal C2 (Brown wire) and ground. If resistance is 5 ohms or less, replace inadvertent power relay. If resistance is greater than 5 ohms, check for open in Brown wire between inadvertent power relay and PZM. If circuit is okay, replace PZM.
4. Disconnect PZM connector. Remove inadvertent power relay. Using DVOM, check resistance between inadvertent power relay connector terminal C2 (Brown wire) and ground. If resistance is 5 ohms or less, repair short to ground in Brown wire between inadvertent power relay and PZM. If resistance is greater than 5 ohms, replace PZM.

DTC B1972, LOW POWER CONTROL FAULT

Controlled power relay supplies power to modules during controlled power usage. For 15 minutes after ignition is turned to LOCK position and PZM is awake, high power control output is grounded. After 15 minutes, low power control output is turned on. Low power control output will supply 2 amps of current for up to 72 hours. If PZM detects more than 2 amps of current is needed, PZM will wake-up and turn on high power control output.

DTC B1972 will set when low power control output is low after 2 consecutive monitoring cycles. When DTC B1972 is set, PZM will turn low power control output off until ignition state changes or PZM wakes-up. DTC B1972 will clear when ignition state changes or PZM wakes-up.

Turn ignition switch to OFF position. Disconnect PZM connector. Remove 10-amp PZM fuse located in trunk compartment fuse block. Using DVOM, check resistance between PZM connector terminal B11 (Orange wire) and ground. If resistance is 5 ohms or less, repair short to ground in Orange wire between 10-amp PZM fuse and PZM. If resistance is greater than 5 ohms, replace PZM.

DTC B1973, HIGH POWER CONTROL FAULT

Controlled power relay supplies power to modules during controlled power usage. For 15 minutes after ignition is turned to LOCK position and PZM is awake, high power control output is grounded. After 15 minutes, low power control output is turned on. Low power control output will supply 2 amps of current for up to 72 hours. If PZM detects more than 2 amps of current is needed, PZM will wake-up and turn on high power control output.

DTC B1973 will set when high power control voltage does not match that of feedback voltage for 2 seconds. When DTC B1973 is set, PZM will turn low power control output off if ignition is in LOCK, OFF or ACC position. DTC B1973 will clear when PZM does not detect malfunction for one monitoring cycle.

1. Remove controlled power relay. Turn ignition switch to ON position. Using DVOM, check voltage between controlled power relay connector terminal C5 (Orange wire) and ground. If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Orange wire between controlled power relay, PZM and trunk compartment fuse block.
2. Using DVOM, check resistance between controlled power relay connector terminal B7 (Black wire) and ground. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open in Black wire between controlled power relay and PZM.
3. Disconnect PZM connectors. Using DVOM, check resistance between controlled power relay connector terminal B7 (Black wire) and ground. If resistance is 5 ohms or less, repair short to ground in Black wire between controlled power relay and PZM. If resistance is greater than 5 ohms, replace controlled power relay.

DTC B1981, BATTERY VOLTAGE TOO LOW

Battery voltage is supplied to PZM at 24-pin connector C1 terminal B3 (Orange wire). PZM utilizes voltage to perform all PZM functions. PZM constantly measures this battery voltage signal. DTC B1981 will set when PZM receives a value greater than 1500 RPM from PCM, and battery voltage measured at PZM connector C1 terminal B3 is less than 10 volts for 2 seconds. DTC B1981 will clear when battery voltage is greater than 10 volts in the next monitoring cycle.

1. Turn ignition switch to OFF position. Connect scan tool. Turn ignition switch to RUN position. Using scan tool, select DATA LIST. Select DATA. Observe voltage displayed on scan tool. If voltage is greater than 10 volts, replace PZM. If voltage is 10 volts or less, go to next step.
2. Check for instrument panel DTCs. See appropriate «INSTRUMENT PANEL»(/cadillac/eldorado/x-1992-2002/remont/gauges-instrument-panels/#instrument-panel) article. If DTC IP1981 does not exist, go to next step. If DTC IP1981 exists, diagnose charging system. See appropriate «GENERATOR & REGULATOR»(/cadillac/eldorado/x-1992-2002/remont/charging-system/#charging-system) article in ELECTRICAL section.
3. Disconnect PZM connector. Using DVOM, check voltage between PZM 32-pin connector C2 terminal B3 (Orange wire) and ground. If voltage is 10 volts or more, replace PZM. If voltage is less than 10 volts, repair high resistance in Orange wire between PZM and trunk compartment fuse block.

DTC B1982, BATTERY VOLTAGE TOO HIGH

Note. DTC B1982 may set if vehicle is connected to a battery charger on fast or boost charge.

Battery voltage is supplied to PZM at 24-pin connector C1 terminal B3 (Orange wire). PZM utilizes voltage to perform all PZM functions. PZM constantly measures this battery voltage signal. DTC B1982 will set when battery voltage measured is greater than 15.5 volts for 4 monitoring cycles. When DTC B1982 is set, Class 2 loss of serial data DTCs will not be set. DTC B1982 will clear when battery voltage is less than 15.5 volts in the next monitoring cycle.

Turn ignition switch to OFF position. Connect scan tool and select DATA LIST. Select DATA. Observe voltage displayed on scan tool. If voltage is 15.5 volts or less and B1982 is current, replace PZM. If voltage is greater than 15.5 volts, repair charging system. See appropriate GENERATOR & REGULATOR article in ELECTRICAL section.

DTC B1983, SOURCE VOLTAGE TOO LOW

Battery voltage is supplied to PZM at 24-pin connector C1 terminal B3 (Orange wire). PZM utilizes voltage to perform all PZM functions. PZM constantly measures this battery voltage signal. DTC B1983 will set when battery voltage measured at PZM connector C1 terminal B3 is less than 9 volts for 4 monitoring cycles and DTC B1981 is not set. When DTC B1983 is set, Class 2 loss of serial data DTCs will not be set. DTC B1983 will clear when battery voltage is greater than 9.5 volts in the next monitoring cycle.

Turn ignition switch to OFF position. Connect scan tool and select DATA LIST. Select DATA. Observe voltage displayed on scan tool. If voltage is 9.4 volts or more and B1983 is current, replace PZM. If voltage is 9 volts or less, repair charging system. See appropriate GENERATOR & REGULATOR article in ELECTRICAL section.

DTC B2470, DAYTIME RUNNING LIGHTS FAULT

Daytime Running Lights (DRL) are commanded on and off by PZM through DRL relay. DRL are activated when ignition switch is in RUN or START position, twilight sentinel is not active, headlights and foglights are off, and transmission is not in Park. When DRL relay is energized, high beams are placed in a series circuit which provides lower illumination for DRL.

A short to ground will be tested when ignition switch is in ON position, DRL are inactive, and IPC verifies vehicle is equipped with DRL. A short to voltage will be tested when ignition switch is in OFF position, DRL are active, and IPC verifies vehicle is equipped with DRL.

DTC B2470 will set when commanded state of DRL does not match feedback state. When DTC B2470 is set, PZM will continue to command state requested until it is achieved or changes. DTC B2470 will clear when commanded state matches feedback state for 2 consecutive monitoring cycles.

1. Turn ignition switch to ON position. Remove DRL relay. Using DVOM, check voltage between DRL relay connector terminal B7 (Light Green/Black wire) and ground. If voltage is one volt or less, go to step 3). If voltage is greater than one volt, go to next step.
2. Turn ignition switch to OFF position. Ensure headlights are turned off. Disconnect PZM connector. Using DVOM, check voltage between DRL relay connector terminal B7 (Light Green/Black wire) and ground. If voltage is one volt or less, replace PZM. If voltage is greater than one volt, repair short to voltage in Light Green/Black wire between PZM and DRL relay.
3. Using DVOM, check voltage between DRL relay connector terminal A9 (Pink wire) and ground. If voltage is one volt or less, go to next step. If voltage is greater than one volt, repair open or short to ground in Pink wire between DRL relay and engine compartment fuse/relay center.
4. Turn ignition switch to OFF position. Disconnect PZM connector. Using DVOM, check resistance between DRL relay connector terminal B7 (Light Green/Black wire) and ground. If resistance is 5 ohms or less, repair short to ground in Light Green/Black wire between PZM and DRL relay. If resistance is greater than 5 ohms, check for malfunctioning DRL relay. See appropriate wiring diagram in DAYTIME RUNNING LIGHTS article. If relay is okay, replace PZM.

DTC B2471, INTERIOR LIGHTS FAULT

Interior lights are commanded by PZM through an output to courtesy lights relay. When courtesy lights relay is energized, ground is provided for interior lights.

A short to ground will be tested when inadvertent power is active, interior lights output is inactive, and DTC B1971 is not set as current. A short to voltage will be tested when inadvertent power is active, interior lights output is active, and DTC B1971 is not set as current.

DTC B2471 will set when commanded state of interior lights does not match feedback state. When DTC B2471 is set, PZM will continue to command state requested until IPC revokes request. DTC B2471 will clear when commanded state matches feedback state.

1. Open vehicle door. If interior lights are on, go to step 3). If interior lights are not on, go to next step.
2. Remove courtesy relay. Disconnect PZM connector. Using DVOM, check resistance between courtesy relay connector terminal B7 (Dark Blue wire) and ground. If resistance is 5 ohms or less, repair short to ground in Dark Blue wire between PZM and courtesy relay. If resistance is greater than 5 ohms, replace PZM.
3. Remove courtesy relay. Using DVOM, check voltage between courtesy relay connector terminal A9 (Orange wire) and ground. If voltage is greater than one volt, go to next step. If voltage is one volt or less, repair open or short to ground in Orange wire between courtesy relay and engine compartment fuse/relay center.
4. Check voltage between courtesy relay connector terminal B7 (Dark Blue wire) and ground. If voltage is one volt or less, replace courtesy relay. If voltage is greater than one volt, check for short to voltage in Dark Blue wire between PZM and courtesy relay. If circuit is okay, replace PZM.

DTC B2472, LOW BEAM OUTPUT FAULT

Low beams are commanded by PZM through an output to headlight relay. When output is grounded, headlight input to IPC is also grounded.

A short to ground will be tested when exterior lights power is active, low beam output is inactive, headlight switch is not active, and DTC B1970 is not set as current. A short to voltage will be tested when exterior lights power is active, low beam output is active, and DTC B1970 is not set as current.

DTC B2472 will set when commanded state of low beams does not match feedback state. When DTC B2472 is set, PZM will continue to command state requested until IPC revokes request. DTC B2472 will clear when commanded state matches feedback state.

1. Turn ignition switch to ON position. Turn headlight switch off. Connect scan tool and select BCM TEST. Select LIGHTS, then select LOW BEAM. Using scan tool, turn low beams on, then off. If headlights are not illuminated, go to next step. If headlights are illuminated, go to step 4).
2. Turn headlight switch on. If headlights illuminate, go to next step. If headlights do not illuminate, check for open in Yellow wire between headlight relay and 16-pin connector C201 (located behind left side of instrument panel, near steering column support). If circuit is okay, replace headlight relay.
3. Cycle ignition. If DTC B2472 is current, check for open in Yellow wire between headlight relay, headlight switch and IPC. If circuit is okay, replace PZM. If DTC B2472 is now history, repair intermittent short to voltage in Yellow wire between headlight relay, headlight switch and IPC.
4. Disconnect 16-pin connector C201, located behind left side of instrument panel, near steering column support. Using scan tool, turn low beams off. If headlights do not illuminate, go to next step. If headlights illuminate, check for short to ground in Yellow wire between headlight relay, headlight switch and IPC. If circuit is okay, replace PZM.
5. Disconnect headlight switch connector. Using DVOM, check resistance between headlight switch connector C1 terminal "C" (Yellow wire) and ground. If resistance is greater than 5 ohms, replace headlight switch. If resistance is 5 ohms or less, check for short to ground in Yellow wire between headlight relay, headlight switch and IPC. If circuit is okay, replace IPC. See appropriate «INSTRUMENT PANEL»(/cadillac/eldorado/x-1992-2002/remont/gauges-instrument-panels/#instrument-panel) article.

DTC B2473, HIGH BEAM OUTPUT FAULT

High beams are commanded by PZM through an output to LO/HI beam control relay. When headlight relay is energized, LO/HI beam control relay provides power source to low beams or high beams. DTC B2473 will set when commanded state of high beams does not match feedback state. When DTC B2473 is set, PZM will continue to command state requested until IPC revokes request. DTC B2473 will clear when commanded state matches feedback state.

1. Turn ignition switch to ON position. Turn headlight switch on. Connect scan tool and select BCM TEST. Select LIGHTS, then select HIGH BEAM. Using scan tool, turn high beams on, then off. If high beams are not illuminated, go to step 4). If high beams are illuminated, go to next step.
2. Turn ignition switch to OFF position. Remove HI/LO beam control relay. Disconnect PZM connector. Using DVOM, check voltage between HI/LO beam control relay connector terminal C9 (Orange wire) and ground. If voltage is one volt or less, go to next step. If voltage is greater than one volt, repair open or short to ground in Orange wire between HI/LO beam control and trunk compartment fuse block.
3. Disconnect PZM connector. Using DVOM, check resistance between HI/LO beam relay connector terminal D7 (Black/White wire) and ground. If resistance is 5 ohms or less, repair short to ground in Black/White wire between PZM and HI/LO beam relay. If resistance is greater than 5 ohms, check for malfunctioning HI/LO beam relay. See appropriate wiring diagram in HEADLIGHT SYSTEMS article. If relay is okay, replace PZM.
4. If high beams turned on in step 1), replace PZM. If high beams did not turn on in step 1), go to next step.
5. Remove HI/LO beam relay. Using DVOM, check voltage between HI/LO beam relay connector terminal C9 (Orange wire) and ground. If voltage is greater than one volt, go to next step. If voltage is one volt or less, repair open or short to ground in Orange wire between HI/LO beam relay and trunk compartment fuse block.
6. Using scan tool, turn high beams on. Check resistance between HI/LO beam relay connector terminal D7 (Black/White wire) and ground. If resistance is 5 ohms or less, replace HI/LO beam relay. If resistance is greater than 5 ohms, check for open in Black/White wire between PZM and HI/LO beam relay.

DTC B2476, PARKING LIGHTS OUTPUT FAULT

Parking lights are commanded by PZM through an output to parking light relay. When output is grounded, parking light input to IPC is also grounded.

A short to ground will be tested when exterior lights power is inactive, parking light output is active, headlight switch is not active, and DTC B1970 is not set as current. A short to voltage will be tested when exterior lights power is active, parking light output is active, and DTC B1970 is not set as current.

DTC B2476 will set when commanded state of parking lights does not match feedback state. When DTC B2476 is set, PZM will continue to command state requested until IPC revokes request. DTC B2476 will clear when commanded state matches feedback state.

1. Turn ignition switch to ON position. Turn headlight switch off. Connect scan tool and select BCM TEST. Select LIGHTS, then select PARKLIGHT. Using scan tool, turn parking lights on, then off. If parking lights are not illuminated, go to step 4). If parking lights are illuminated, go to next step.
2. Turn ignition switch to OFF position. Disconnect headlight switch connector. Using DVOM, check resistance between headlight switch connector C1 terminal "E" (Gray/Black wire) and ground. If resistance is greater than 5 ohms, go to next step. If resistance is 5 ohms or less, check for short to ground in Gray/Black wire between PZM and headlight switch. If circuit is okay, replace PZM.
3. Check resistance between headlight switch connector C1 terminal "D" (Light Blue wire) and ground. If resistance is greater than 5 ohms, replace headlight switch. If resistance is 5 ohms or less, check for short to ground in Light Blue wire between headlight switch and IPC. If circuit is okay, replace IPC. See appropriate «INSTRUMENT PANEL»(/cadillac/eldorado/x-1992-2002/remont/gauges-instrument-panels/#instrument-panel) article.
4. If parking lights did not turn on in step 1), go to next step. If parking lights turned on in step 1), replace PZM.
5. Remove parking light relay. Disconnect PZM connector. Using DVOM, check resistance between PZM 32-pin connector C2 terminal C12 (Gray/Black wire) and parking light relay terminal B4 (Gray/Black wire). If resistance is greater than 5 ohms, repair open in Gray/Black wire between parking light relay and PZM. If resistance is 5 ohms or less, replace PZM.

DTC B2477, REVERSE RELAY SHORTED TO GROUND

When PZM receives input that transaxle is in reverse, PZM energizes reverse relay which will turn on back-up lights. When back-up lights have been commanded on, PZM constantly measures voltage at 32-pin connector C2 terminal D3 (Dark Green wire). DTC B2477 will set when voltage is approximately equal to ground. DTC B2477 will clear when voltage is greater than ground for at least one monitoring cycle.

If DTC B2477 is set, check for short to ground in Dark Green wire between PZM connector C2 terminal D3 and reverse relay (located in trunk #5 micro relay center).

DTC B2478, REVERSE RELAY SHORTED TO VOLTAGE

When PZM receives input that transaxle is in Reverse, PZM energizes reverse relay which will turn on back-up lights. When back-up lights have been commanded on, PZM constantly measures voltage at 32-pin connector C2 terminal D3 (Dark Green wire). DTC B2478 will set when voltage is not at ground potential for at least 2 seconds. DTC B2478 will clear when voltage is greater than ground for at least one monitoring cycle.

If DTC B2478 is set, check for short to voltage in Dark Green wire between PZM connector C2 terminal D3 and reverse relay (located in trunk #5 micro relay center).

DTC B2502, PARK RELAY (BTSI) SHORTED TO GROUND

When transaxle is in Park, PZM controls park relay output low to enable Brake Transaxle Shift Interlock (BTSI). PZM will continuously monitor this voltage. DTC B2502 will set when park relay output is not active, IGN-1 input exists, and PZM determines output is low for 2 consecutive monitoring cycles. DTC B2502 will clear when park relay output is not active, IGN-1 input exists, and PZM determines output is high for one monitoring cycle.

If DTC B2502 is set, check for short to ground in Orange/Black wire between PZM 32-pin connector C2 terminal C16 and park relay (located in trunk #5 micro relay center).

DTC B2503, PARK RELAY (BTSI) SHORTED TO VOLTAGE

When transaxle is in Park, PZM controls park relay output low to enable Brake Transaxle Shift Interlock (BTSI). PZM will continuously monitor this voltage. DTC B2503 will set when park relay output is active and PZM determines output is high for 2 consecutive monitoring cycles. DTC B2503 will clear when park relay output is active and PZM determines output is low for 2 monitoring cycles.

If DTC B2503 is set, check for short to voltage in Orange/Black wire between PZM 32-pin connector C2 terminal C16 and park relay (located in trunk #5 micro relay center).

DTC B2550, STORAGE MODE ENTERED

To conserve power, PZM can be commanded into a storage mode. DTC B2550 will set 20 minutes after storage mode has been entered. DTC B2550 will clear when ignition switch is turned from LOCK position.

DTC B2719, UTD - TRUNK TAMPER SWITCH FAULT

A test is run to determine if trunk tamper switch is active when PZM is in a off, idle, ready to arm, arm initiated or arm delay state. DTC B2719 will set when PZM determines trunk tamper switch has been active for 2 seconds. When DTC B2719 is set, UTD will still arm, disregarding input from trunk tamper switch. DTC B2719 will clear when PZM does not determine trunk tamper switch as active for 2 consecutive monitoring cycles.

1. Turn ignition switch to OFF position. Disconnect PZM connector. Using DVOM, check resistance between PZM 24-pin connector C1 terminal A3 (Light Blue wire) and ground. If resistance is greater than 5 ohms, replace PZM. If resistance is 5 ohms or less, go to next step.
2. Disconnect trunk tamper switch connector. Using DVOM, check resistance between trunk tamper switch connector terminal "A" and ground. If resistance is greater than 5 ohms, replace trunk tamper switch. If resistance is 5 ohms or less, repair short to ground in Light Blue wire between trunk tamper switch and PZM.

Removal

Disconnect negative battery cable. Remove 10-amp COMFORT fuse located in trunk compartment fuse block. Remove rear seat cushion. Remove rear seat back. Locate BCM in trunk, on electronic module center, attached to back of rear seat. (Scheme 4) Disconnect BCM harness connectors. Remove BCM from vehicle.

Installation

Install BCM and reconnect harness connectors. Install rear seat back and cushion. Install 10-amp COMFORT fuse in trunk compartment fuse block. Reconnect negative battery cable.

Scheme 4

See also:
• TESTS W/CODES
• INSTRUMENT PANEL
• A/C SYSTEM GENERAL SERVICING
• GENERATOR & REGULATOR
• SERVICE MODE OPERATION
• WIRING DIAGRAM