Body Control Module Cadillac DeVille Concours

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, and ignition accessory (ACC). BCM uses 2 separate data lines, the UART (Universal Asynchronous Receiver/Transmitter) and class 2, to communicate with other system control modules. UART system uses a master and remote transmitter communication process. BCM is the master and controls signals on serial data line by soliciting remote transmitters (system control modules) for information, then waits for correct response. UART remote transmitter control modules include: Electronic Brake and Traction Control Module (EBTCM), Continuously Variable Road Sensing Suspension (CVRSS), Road Sensing Suspension (RSS), and Sensing and Diagnostic Module (SDM).

Class 2 system uses a peer-to-peer communication process and is transmitted at a much higher rate than the UART system. Class 2 control modules include: Air Control Module (ACM), Body Control Module (BCM), Cellular Telephone (PHN), Climate Control Panel (CCP), Instrument Panel Cluster (IPC), Integrated Radio Controller (IRC), Powertrain Control Module (PCM), memory seat/memory mirror module, and Remote Function Actuator (RFA). BCM acts as an interpreter for data communication between UART and class 2 to satisfy need for communication of serial data between modules.

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 6 digit alphanumeric code beginning with "PZ". Malfunctions are recorded as history/intermittent failures or as current failures. Codes are displayed in sequential order beginning with lowest number code. If no codes are present for a system, a "NO X CODE" message (with X being system, i.e., "PZ", "IP", etc.) will be displayed. If communication line to a component is not operating, a "NO X DATA" message will be displayed, indicating IPC could not communicate with that system.

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 AUTO/ECON button on CCP, or turn ignition off. Codes will not be cleared. System will return to normal vehicle operation.

Current Failures

Current codes indicate BCM has detected a fault which is currently present. Current codes can be identified by the letter "C" following the code (i.e., PZ1552C, PZ1556C, etc.).

History/Intermittent Failures

History/intermittent codes indicate BCM previously detected a fault which later disappeared. History/intermittent codes can be identified by the letter "H" following the code (i.e., PZ1552H, PZ1556H, etc.). If a history/intermittent code is set, fault may be intermittent or the system for which the code is set may not be currently operating.

Intermittent failures may be caused by problems with electrical circuit. If a visual inspection does not locate problem, vehicle may be driven with a DVOM attached to suspect circuit. Abnormal voltage or resistance readings when problem occurs may indicate problem is within that circuit.

ENTERING & EXITING DIAGNOSTICS

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 Sensing 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 buttons on Climate Control Panel (CCP). Continue pressing OFF and WARMER 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. 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, SDM, 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.
4. To exit diagnostic mode, press DEFOG or AUTO/ECON 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, SDM, 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 following actions may be taken to control display: Pressing LO (fan down) button on CCP will display next available system selection (i.e., SDM?, 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. Pressing HI (fan up) button on CCP will select displayed system for testing (i.e., PZM DATA, PZM INPUTS, PZM OUTPUTS, etc.). (Scheme 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: 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) 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. 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.

PZM SNAPSHOT

Selection of SNAPSHOT test type will allow the recall of all "DATA" and "INPUT" values for the selected system from specific point in time. These values may be retrieved for either a snapshot that was manually triggered or, if the selected system allows, a snapshot from the setting of last PZM trouble code.

Snapshot may be selected by pressing HI button on CCP. If snapshot for a set PZM trouble code is present, display will read "PXXX" (XXX being 3-digit code) when snapshot is first selected. Snapshot can be by-passed by pressing LO button. This selection process may continue until all stored PZM codes with snapshot information are displayed. At this point, the manual snapshot display "TAKE SNAPSHOT?" will appear. Pressing LO button will return system to start of snapshot process, if desired.

If no stored PZM codes are available or all stored codes with snapshot information are by-passed, display will read "TAKE SNAPSHOT?". A manually triggered snapshot may be taken at this point by pressing the HI button. Display will read "SNAPSHOT TAKEN" and will change to "SNAP DATA?" within several seconds.

VIEWING SNAPSHOT INFORMATION

After snapshot has been taken or a code set snapshot selected, display will read "SNAP DATA?" or "PXXX DATA". Any of following actions may be taken to control display.

Pressing HI button on CCP will select data values for the snapshot. At this point, display is controlled as it would be for non-snapshot data displays, however; all values represent memorized vehicle conditions.

Pressing LO button will allow snapshot INPUT values to be selected. Display will read "SNAP INPUTS" or "PXXX INPUTS".

Pressing OFF button on CCP will return to original snapshot screen. Pressing OFF button several times will return display to next available test selection.

BCM DTC DEFINITION

BCM DTC DEFINITION

BCM LOCATION

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

DIAGNOSING & REPAIRING BCM DTCS

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

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

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

DTC PZ1552, LOSS OF PZM KEEP ALIVE MEMORY (KAM)

DTC PZ1552 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 PZ1552 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. Low Power State - Set To Unknown
6. Power Down Hours - Clear
7. Shutdown - No Controlled Power Shutdown
8. Storage Mode State - Disable
9. Key Cylinder State - Inactive
10. Class 2 Bus State - Unknown
11. Driver Door Jamb - Closed
12. Other Doors Jamb - Closed
13. Ignition State - Current State

If DTC PZ1552 is set and battery was not disconnected, check for poor connections at PZM connector power and ground terminals.

DTC PZ1556, PZM EEPROM WRITE ERROR

DTC PZ1556 testing is run for each write block of writes to EEPROM. PZM writes to EEPROM cell and then reads data back. DTC PZ1556 will set when data read by PZM does not match data written to EEPROM after 2 consecutive attempts. DTC PZ1556 will clear when data read by PZM matches data written to EEPROM. If DTC PZ1556 is set, clear DTCs and cycle ignition. If DTC PZ1556 sets, replace PZM.

DTC PZ1558, PZM EEPROM CHECKSUM ERROR

Within 2.5 seconds after ignition switch is turned to RUN position, PZM adds the checksum of EEPROM block. DTC PZ1558 will set when value of addition does not equal zero. When DTC PZ1558 is set, PZM will clear all codes, set DTC PZ1558 as current and default to the following

1. Supplemental Inflatable Restraint (SIR) - No Change
2. Personalization - Factory Default
3. Ignition Cycle Counter - Zero
4. Theft Alarm Condition - Cleared

If DTC PZ1558 is set, clear DTCs and cycle ignition. If DTC PZ1558 sets, replace PZM.

DTC PZ1970, EXTERIOR LIGHT POWER FAULT

PZM commands exterior lights on by energizing headlight and parking light relays. DTC PZ1970 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 PZ1970 is set, PZM will command exterior lights off, then attempt to turn exterior lights on until lights are no longer required. DTC PZ1970 will clear when exterior lights are commanded on and PZM senses exterior light power on after 2 consecutive monitoring cycles.

Testing

1. Turn ignition switch to OFF position. Remove parking light relay and headlight relay. Using DVOM, measure resistance between parking light relay connector terminal No. 86 and ground. If resistance is greater than 5 ohms, go to step 3). If resistance is 5 ohms or less, go to next step.
2. Repair short to ground in exterior light power circuit between parking light relay and PZM. Turn ignition switch to ON position. Turn headlights on. Check for DTC PZ1970. If DTC PZ1970 is present, replace PZM. If DTC PZ1970 is not present, system is functioning properly.
3. Install headlight relay. Using DVOM, measure resistance between parking light relay connector terminal No. 86 and ground. If resistance is 5 ohms or less, replace headlight relay. If resistance is greater 5 ohms, go to next step.
4. Install parking light relay. Remove headlight relay. Using DVOM, measure resistance between headlight relay connector terminal No. 86 and ground. If resistance is 5 ohms or less, replace parking light relay. If resistance is greater than 5 ohms, replace PZM.

DTC PZ1971, 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 PZ1971 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 PZ1971 is set, PZM will continue to command requested state of relay until it is achieved or no longer necessary. DTC PZ1971 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. Disconnect PZM connector. Remove inadvertent power relay. Using DVOM, measure voltage between inadvertent power relay connector terminal C2 and ground. If voltage is greater than one volt, repair short to battery in inadvertent power circuit between inadvertent power relay and PZM. If voltage is one volt or less, go to next step.
3. Using DVOM, measure resistance between inadvertent power relay connector terminal A1 and 10-amp MIRROR fuse located in engine compartment fuse/relay block. If resistance is greater than 5 ohms, repair open in fuse circuit between inadvertent power relay and 10-amp MIRROR fuse. If resistance is 5 ohms or less, replace PZM.
4. Disconnect PZM connector. Remove inadvertent power relay. Using DVOM, measure resistance between inadvertent power relay connector terminal C2 and ground. If resistance is 5 ohms or less, repair short to ground in inadvertent power circuit between inadvertent power relay and PZM. If resistance is greater than 5 ohms, replace PZM.

DTC PZ1972, 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 and 20 minutes. If PZM detects more than 2 amps of current is needed, PZM will wake-up and turn on high power control output.

DTC PZ1972 will set when, PZM does not detect low power control output "on" after 300 milliseconds. When DTC PZ1972 is set, PZM will turn low power control output off until ignition state changes and PZM wakes-up. DTC PZ1972 will clear when, ignition state changes and PZM wakes-up.

1. Turn ignition switch to OFF position. Disconnect PZM connector. Using DVOM, measure resistance between PZM connector terminal B11 and ground. If resistance is greater than 5 ohms, replace PZM. If resistance is 5 ohms or less, go to next step.
2. Remove 10-amp PZM fuse located in trunk compartment fuse block. Using DVOM, measure resistance between PZM connector terminal B11 and ground. If resistance is 5 ohms or less, repair short to ground in low power control output circuit between 10-amp PZM fuse and PZM. If resistance is greater than 5 ohms, go to next step.
3. Install 10-amp PZM fuse. Remove 20-amp CLUSTER fuse, 10-amp RADIO/PHONE fuse and 30-amp AMP fuse, all located in trunk compartment fuse block. Using DVOM, measure resistance between PZM connector terminal B11 and ground. If resistance is 5 ohms or less, repair short to ground in controlled power relay circuit between 20-amp CLUSTER fuse, 10-amp RADIO/PHONE fuse, 30-amp AMP fuse and controlled power relay. If resistance is greater than 5 ohms, go to next step.
4. Install 10-amp RADIO/PHONE fuse. Using DVOM, measure resistance between PZM connector terminal B11 and ground. If resistance is 5 ohms or less, repair short to ground in fuse circuit between 10-amp RADIO/PHONE fuse and accessory time delay cut-off relay. If resistance is greater than 5 ohms, go to next step.
5. Install 20-amp CLUSTER fuse. Using DVOM, measure resistance between PZM connector terminal B11 and ground. If resistance is 5 ohms or less, repair short to ground in fuse circuit between 20-amp CLUSTER fuse and instrument panel cluster. If resistance is greater than 5 ohms, repair short to ground in fuse circuit between 30-amp AMP fuse and audio relay or amplifier.

DTC PZ1973, 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 and 20 minutes. If PZM detects more than 2 amps of current is needed, PZM will wake-up and turn on high power control output. High power control output test can only be performed with ignition switch in LOCK position.

DTC PZ1973 will set when, PZM detects battery voltage with ignition switch in LOCK position. When DTC PZ1973 is set, PZM will turn low power control output off. DTC PZ1973 will clear when, PZM does not detect malfunction for one monitoring cycle.

1. Turn ignition switch to OFF position. Disconnect PZM connector. Using DVOM, measure voltage between PZM connector terminal D1 and ground. If voltage is one volt or less, replace PZM. If voltage is greater than one volt, go to next step.
2. Remove controlled power relay. Using DVOM, measure voltage between controlled power relay connector terminal B7 and ground. If voltage is one volt or less, replace PZM. If voltage is greater than one volt, repair short to battery in high power control output circuit between controlled power relay and PZM.

DTC PZ1981, BATTERY VOLTAGE TOO LOW

Battery voltage is supplied to PZM. PZM utilizes voltage to perform all PZM functions. PZM constantly measures this battery voltage signal. DTC PZ1981 will set when, PZM receives a value greater than 1500 RPM from PCM and battery voltage measured is less than 10 volts for 2 seconds. DTC PZ1981 will clear when, battery voltage is greater than 10 volts.

1. Turn ignition switch to OFF position. Connect scan tool and 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. Disconnect PZM connector. Using DVOM, measure voltage between PZM connector terminal B3 and ground. If voltage is greater than 10 volts, replace PZM. If voltage is 10 volts or less, repair charging system. See «GENERATOR & REGULATOR»(/cadillac/deville-concours/1994-1998/remont/charging-system/#charging-system) article in ELECTRICAL section.

DTC PZ1982, BATTERY VOLTAGE TOO HIGH

Battery voltage is supplied to PZM. PZM utilizes voltage to perform all PZM functions. PZM constantly measures this battery voltage signal. DTC PZ1982 will set when, battery voltage measured is greater than 16 volts for 2 seconds. DTC PZ1982 will clear when, battery voltage is less than 16 volts.

1. Turn ignition switch to OFF position. Connect scan tool and select DATA LIST. Select DATA. Observe voltage displayed on scan tool. If voltage is less than 16 volts, replace PZM. If voltage is 16 volts or more, go to next step.
2. Disconnect PZM connector. Using DVOM, measure voltage between PZM connector terminal B3 and ground. If voltage is less than 16 volts, replace PZM. If voltage is 16 volts or more, repair charging system. See «GENERATOR & REGULATOR»(/cadillac/deville-concours/1994-1998/remont/charging-system/#charging-system) article in ELECTRICAL section.

DTC PZ2016, LOSS OF SERIAL COMMUNICATIONS - PCM

Every 5 seconds while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to Powertrain Control Module (PCM), indicating system is operating properly. Signal is then transmitted to PZM. DTC PZ2016 will set when PZM does not receive signal from PCM after 3 consecutive monitoring cycles. DTC PZ2016 will clear when PCM transmits signal to PZM.

If multiple class 2 codes are set as current (i.e., PZ2016, PZ2096, PZ2128, PZ2152, PZ2153), check for short to ground or battery in circuit between PCM and individual control modules.

1. Ensure PCM is operating properly. If PCM is not operating properly, diagnose and repair as necessary. See «TESTS W/CODES»(/cadillac/deville-concours/1994-1998/remont/testing-diagnostics/#engine-control-system-tests-wcodes) . If PCM is okay, turn ignition switch to OFF position. Disconnect C205 23-pin connector located behind right side of dash, near kick panel. Disconnect PCM connector C1. Using DVOM, measure resistance between PCM connector C1, terminal No. 59 and C205 connector, terminal "C". If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open in circuit between PCM and C205 connector.
2. Disconnect HVAC programmer connector. Using DVOM, measure resistance between HVAC programmer connector terminal D4 and C205 connector, terminal "C" If resistance is greater than 5 ohms, replace PCM. If resistance is 5 ohms or less, repair open in circuit between C205 connector and splice S324 located under right front seat, on right rail.

DTC PZ2042, LOSS OF SERIAL COMMUNICATIONS - ABS/TCS

PZM transmits UART data signals to controllers for bus and maintains a counter which increments with each signal to control module. When control module responds to signal, counter is cleared. PZ2042 will set when PZM signal counter for device exceeds 20. When DTC PZ2042 is set, PZM will send a class 2 signal to instrument panel cluster to illuminate TRACTION CONTROL indicator. DTC PZ2042 will clear when PZM does not detect a malfunction for one monitoring cycle.

If DTC PZ2056 and PZ2088 are also set as current, check for short to ground or battery in circuit between control modules. Ensure anti-lock brake/traction control system is operating properly with exception of loss of communication. If anti-lock brake system/traction control system is not operating properly, repair as necessary. See appropriate ANTI-LOCK/TCS article. If anti-lock brake system/traction control system is okay, check for poor connections at Electronic Brake and Traction Control Module (EBTCM). If connections are okay, replace EBTCM.

DTC PZ2056, LOSS OF SERIAL COMMUNICATIONS - RSS

PZM transmits UART data signals to controllers for bus and maintains a counter which increments with each signal to control module. When control module responds to signal, counter is cleared. PZ2056 will set when PZM signal counter for device exceeds 20. When DTC PZ2056 is set, PZM will send a class 2 signal to instrument panel cluster to display SERVICE RIDE CONTROL message. DTC PZ2056 will clear when PZM does not detect a malfunction for one monitoring cycle.

If DTC PZ2042 and PZ2088 are also set as current, check for short to ground or battery in circuit between control modules. Ensure road sensing suspension system is operating properly with exception of loss of communication. If road sensing suspension system is not operating properly, repair as necessary. See SUSPENSION article. If road sensing suspension system is okay, check for poor connections at RSS or Continuously Variable Road Sensing Suspension (CVRSS) module. If connections are okay, replace RSS or CVRSS module.

DTC PZ2088, LOSS OF SERIAL COMMUNICATIONS - SIR

PZM transmits UART data signals to controllers for bus and maintains a counter which increments with each signal to control module. When control module responds to signal, counter is cleared. PZ2088 will set when PZM signal counter for device exceeds 20. When DTC PZ2088 is set, PZM will send a class 2 signal to instrument panel cluster to display SERVICE AIR BAG message. DTC PZ2088 will clear when PZM does not detect a malfunction for one monitoring cycle.

If DTC PZ2042 and PZ2056 are also set as current, check for short to ground or battery in circuit between control modules. Ensure supplemental inflatable restraint system is operating properly with exception of loss of communication. If supplemental inflatable restraint system is not operating properly, repair as necessary. See appropriate AIR BAG RESTRAINT SYSTEM article. If supplemental inflatable restraint system is okay, check for poor connections at Sensing and Diagnostic Module (SDM). If connections are okay, replace SDM.

DTC PZ2096, LOSS OF SERIAL COMMUNICATIONS - IPC

Every 5 seconds, while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to Instrument Panel Cluster (IPC) indicating system is operating properly. Signal is then transmitted to PZM. DTC PZ2096 will set when PZM does not receive signal from IPC after 3 consecutive monitoring cycles. DTC PZ2096 will clear when IPC transmits signal to PZM.

If multiple class 2 codes are set as current (i.e., PZ2016, PZ2096, PZ2128, PZ2152, PZ2153), check for short to ground or battery in circuit between IPC and individual control modules.

Ensure IPC is operating properly. If IPC is not operating properly, diagnose and repair as necessary. See the INSTRUMENT PANEL article. If IPC is okay, check for poor connections at IPC. If connections are okay, replace IPC.

DTC PZ2128, LOSS OF SERIAL COMMUNICATIONS - IRC

Every 5 seconds, while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to Integrated Radio Controller (IRC) indicating system is operating properly. Signal is then transmitted to PZM. DTC PZ2128 will set when PZM does not receive signal from IRC after 3 consecutive monitoring cycles. When DTC PZ2128 is set, PZM will send a class 2 signal to instrument panel cluster to display NO IRC DATA message. DTC PZ2128 will clear when IRC transmits signal to PZM.

If multiple class 2 codes are set as current (i.e., PZ2016, PZ2096, PZ2128, PZ2152, PZ2153), check for short to ground or battery in circuit between IRC and individual control modules.

Ensure IRC is operating properly. If IRC is not operating properly, diagnose and repair as necessary. If IRC is okay, check for poor connections at IRC. If connections are okay, replace IRC.

DTC PZ2152, LOSS OF SERIAL COMMUNICATIONS - HVAC PROGRAMMER

Every 5 seconds, while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to Heating, Ventilation and Air Conditioning (HVAC) programmer indicating system is operating properly. Signal is then transmitted to PZM. DTC PZ2152 will set when PZM does not receive signal from HVAC programmer after 3 consecutive monitoring cycles. When DTC PZ2152 is set, PZM will send a class 2 signal to instrument panel cluster to display NO ACM DATA message. DTC PZ2152 will clear when HVAC programmer transmits signal to PZM.

If multiple class 2 codes are set as current (i.e., PZ2016, PZ2096, PZ2128, PZ2152, PZ2153), check for short to ground or battery in circuit between HVAC programmer and individual control modules.

Ensure HVAC programmer is operating properly. If HVAC programmer is not operating properly, diagnose and repair as necessary. See A/C-HEATER SYSTEM - AUTOMATIC article. If HVAC programmer is okay, check for poor connections at HVAC programmer. If connections are okay, replace HVAC programmer.

DTC PZ2153, LOSS OF SERIAL COMMUNICATIONS - CCP

Every 5 seconds, while ignition switch is in RUN position, control modules that communicate on class 2 data bus transmit a performance condition signal to Climate Control Panel (CCP) indicating system is operating properly. Signal is then transmitted to PZM. DTC PZ2153 will set when PZM does not receive signal from CCP after 3 consecutive monitoring cycles. When DTC PZ2153 is set, PZM will send a class 2 signal to instrument panel cluster to display NO CCP DATA message. DTC PZ2153 will clear when CCP transmits signal to PZM.

If multiple class 2 codes are set as current (i.e., PZ2016, PZ2096, PZ2128, PZ2152, PZ2153), check for short to ground or battery in circuit between CCP and individual control modules.

Ensure CCP is operating properly. If CCP is not operating properly, diagnose and repair as necessary. See the INSTRUMENT PANEL article. If CCP is okay, check for poor connections at CCP. If connections are okay, replace CCP.

DTC PZ2255, GENERIC LOSS OF SERIAL DATA (SOURCE ID UNKNOWN)

PZM periodically sends a request for information to other control modules via class 2 data line. DTC PZ2255 will set when PZM requests information on a module and module is not on-line. When DTC PZ2255 is set, PZM will use default values for information requested. DTC PZ2255 will clear when module which information is requested comes back on-line.

If DTC PZ2255 is set, clear DTCs and cycle ignition. If DTC PZ255 sets as current, ensure all control modules are operating properly. Also, check for short to ground or battery in class 2 data bus. If all modules and class 2 data bus are okay, replace PZM.

DTC PZ2470, 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 fog lights 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 battery will be tested when ignition switch is in OFF position, DRL are active, and IPC verifies vehicle is equipped with DRL.

DTC PZ2470 will set when commanded state of DRL does not match feedback state. When DTC PZ2470 is set, PZM will continue to command state requested until it is achieved or changes. DTC PZ2470 will clear when commanded state matches feedback state for 2 consecutive monitoring cycles.

1. Turn ignition switch to ON position. Turn headlights on with high beams. If left high beam is off, go to step 4). If left high beam is on, go to next step.
2. Turn ignition switch to OFF position. Turn headlights off. Remove DRL relay "F". Disconnect PZM connector. Using DVOM, measure voltage between DRL relay "F" connector terminal No. 85 and ground. If voltage is greater than one volt, repair short to battery in daytime running lights circuit between DRL relay "F" and PZM. If voltage is one volt or less, go to next step.
3. Install DRL relay "F". Using DVOM, measure voltage between PZM connector terminal C5 and ground. If voltage is greater than one volt, replace DRL relay "F". If voltage is one volt or less, replace PZM.
4. Turn ignition switch to OFF position. Turn headlights off. Remove DRL relay "F". Disconnect PZM connector. Using DVOM, measure resistance between DRL relay "F" connector terminal No. 86 and ground. If resistance is 5 ohms or less, repair short to ground in daytime running lights circuit between DRL relay "F" and PZM. If resistance is greater than 5 ohms, go to next step.
5. Install DRL relay "F". Disconnect PZM connector. Using DVOM, measure resistance between PZM connector terminal C5 and ground. If resistance is 5 ohms or less, replace DRL relay "F". If resistance is greater than 5 ohms, replace PZM.

DTC PZ2471, 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 PZ1971 is not set as current. A short to battery will be tested when inadvertent power is active, interior lights output is active, and DTC PZ1971 is not set as current.

DTC PZ2471 will set when commanded state of interior lights does not match feedback state. When DTC PZ2471 is set, PZM will continue to command state requested until IPC revokes request. DTC PZ2471 will clear when commanded state matches feedback state.

1. Turn ignition switch to OFF position. Connect scan tool and select BCM TEST. Select LIGHTS, then select INTERIOR LIGHTS. Using scan tool, turn interior lights on. If interior lights illuminate, go to step 4). If interior lights do not illuminate, go to next step.
2. Disconnect PZM connector. Remove courtesy lights relay. Using DVOM, measure voltage between courtesy lights relay connector terminal No. 85 and ground. If voltage is greater than one volt, repair short to battery in interior lights circuit between courtesy lights relay and PZM. If voltage is one volt or less, go to next step.
3. Using DVOM, measure resistance between courtesy lights relay connector terminal No. 86 and 10-amp INT LPS fuse located in engine compartment fuse/relay block. If resistance is greater than 5 ohms, repair open in fuse circuit between courtesy lights relay and 10-amp INT LPS fuse. If resistance is 5 ohms or less, replace PZM.
4. Disconnect PZM connector. Remove courtesy lights relay. Using DVOM, measure resistance between courtesy lights relay connector terminal No. 85 and ground. If resistance is 5 ohms or less, repair short to ground in courtesy lights circuit between courtesy lights relay and PZM. If resistance is greater than 5 ohms, go to next step.
5. Install courtesy lights relay. Using DVOM, measure resistance between PZM connector terminal C13 and ground. If resistance is 5 ohms or less, replace courtesy lights relay. If resistance is greater than 5 ohms, replace PZM.

DTC PZ2472, 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 PZ1970 is not set as current. A short to battery will be tested when exterior lights power is active, low beam output is active, and DTC PZ1970 is not set as current.

DTC PZ2472 will set when commanded state of low beams does not match feedback state. When DTC PZ2472 is set, PZM will continue to command state requested until IPC revokes request. DTC PZ2472 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 do not illuminate, go to step 3). If headlights illuminate, go to next step.
2. Turn ignition switch to OFF position. Remove headlight relay. Using DVOM, measure resistance between headlight relay connector terminal No. 85 and ground. If resistance is 5 ohms or less, repair short to ground in low beam circuit between headlight relay, PZM, headlight switch and IPC. If resistance is greater than 5 ohms, replace PZM.
3. Turn headlight switch on. If headlights do not illuminate, repair open in low beam circuit between headlight relay and 16-pin connector located behind lower left side of dash. If headlights illuminate, go to next step.
4. Turn headlight switch off. Turn ignition switch to OFF position. Disconnect PZM connector. Remove headlight relay. Using DVOM, measure resistance between headlight relay connector terminal No. 85 and PZM connector terminal C9. If resistance is greater than 5 ohms, repair open in low beam circuit between PZM and 16-pin connector located behind lower left side of dash. If resistance is 5 ohms or less, replace PZM.

DTC PZ2473, 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 PZ2473 will set when commanded state of high beams does not match feedback state. When DTC PZ2473 is set, PZM will continue to command state requested until IPC revokes request. DTC PZ2473 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 do not illuminate, go to step 3). If high beams illuminate, go to next step.
2. Turn ignition switch to OFF position. Turn headlight switch off. Disconnect PZM connector. Using DVOM, measure resistance between PZM connector terminal C8 and ground. If resistance is 5 ohms or less, repair short to ground in high beam circuit between LO/HI beam control relay and PZM. If resistance is greater than 5 ohms, replace PZM.
3. Turn ignition switch to OFF position. Turn headlight switch off. Remove LO/HI beam control relay. Disconnect PZM connector. Using DVOM, measure resistance between LO/HI beam control relay connector terminal No. 86 and PZM connector terminal C8. If resistance is greater than 5 ohms, repair open in high beam circuit between LO/HI beam control relay and PZM. If resistance is 5 ohms or less, replace PZM.

DTC PZ2476, 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 PZ1970 is not set as current. A short to battery will be tested when exterior lights power is active, parking light output is active, and DTC PZ1970 is not set as current.

DTC PZ2476 will set when commanded state of parking lights does not match feedback state. When DTC PZ2476 is set, PZM will continue to command state requested until IPC revokes request. DTC PZ2476 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 do not illuminate, go to step 5). If parking lights illuminate, go to next step.
2. Turn ignition switch to OFF position. Using DVOM, measure resistance between headlight switch connector C1, terminal "E" and ground. If resistance is greater than 5 ohms, replace headlight switch. If resistance is 5 ohms or less, go to next step.
3. Disconnect PZM connector. Using DVOM, measure resistance between PZM connector terminal C12 and ground. If resistance is greater than 5 ohms, replace PZM. If resistance is 5 ohms or less, go to next step.
4. Remove parking light relay. Using DVOM, measure resistance between parking light relay connector terminal No. 85 and ground. If resistance is greater than 5 ohms, replace parking light relay. If resistance is 5 ohms or less, repair short to ground in parking light circuit between parking light relay, PZM and headlight switch.
5. Turn headlight switch on. If parking lights illuminate, check for poor connection at PZM. If connection is okay, replace PZM. If parking lights do not illuminate, go to next step.
6. Install parking light relay. Remove headlight relay. Using DVOM, measure resistance between parking light relay connector terminal No. 85 and PZM connector terminal C12. If resistance is greater than 5 ohms, repair open in parking light circuit between parking light relay and PZM. If resistance is 5 ohms or less, replace PZM.

DTC PZ2550, STORAGE MODE ENTERED

To conserve power, PZM can be commanded into a storage mode. DTC PZ2550 will set when storage mode has been entered. DTC PZ2550 will clear when PZM receives a "wake-up" signal.

DTC PZ2719, 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 PZ2719 will set when PZM determines trunk tamper switch has been active for 2 seconds. When DTC PZ2719 is set, UTD will still arm, disregarding input from trunk tamper switch. DTC PZ2719 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, measure resistance between PZM connector terminal A3 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, measure 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 trunk tamper input circuit 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

1. 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.
2. Reprogram PZM override PZ S33 according to following values. K = Seville = 4 Ksp = DeVille/Concours = 5
3. Press and hold DEFROST and AUTO buttons on CCP until display flashes. Cycle ignition. Clear DTCs.

Scheme 4

See also:
• GENERATOR & REGULATOR
• TESTS W/CODES
• INSTRUMENT PANEL
• A/C-HEATER SYSTEM - AUTOMATIC
• WIRING DIAGRAM