Instrument Panel - Analog Buick Century V

DESCRIPTION & OPERATION

The Instrument Panel Cluster (IPC) uses an electric analog speedometer with stepper motor-driven odometer, analog fuel gauge and indicator lights. The IPC is backlit for nighttime illumination. Some models may be equipped with analog coolant temperature gauge, oil pressure gauge and voltmeter. For speedometer testing, see appropriate G - TEST W/CODES article in ENGINE PERFORMANCE.

Note. Some models use a Powertrain Control Module (PCM) rather than an Electronic Control Module (ECM). Aside from electronic engine controls, the modules also differ in that the PCM controls electronic transmission internals and cruise control system. Unless specifically stated, references to ECM also apply to PCM-equipped vehicles.

BRAKE SYSTEM WARNING INDICATOR

The brake system warning indicator illuminates when brake hydraulic pressure is lost. With ignition switch slowly turned past RUN position, brake indicator should illuminate before ignition switch reaches START position. With ignition switch in RUN position and parking brake engaged, brake indicator should illuminate.

BRIGHT HEADLIGHT INDICATOR

The BRIGHT headlight indicator illuminates when headlights are on and high beams are selected.

COOLANT TEMPERATURE INDICATOR

The TEMP indicator illuminates when engine coolant temperature exceeds approximately 258°F (126°C). The indicator will turn off when engine coolant temperature drops to less than 241°F (116°C). The TEMP indicator illuminates as a bulb test when ignition switch is in RUN or START position.

COOLANT TEMPERATURE GAUGE

With ignition switch in RUN position, gauge indicates approximate engine coolant temperature. Gauge has 2 magnetic coils which pull on pointer in opposite directions. This balancing effect of the coils prevents possible errors resulting from varying battery voltage. Both coils have voltage applied directly and "cold" coil is permanently grounded. "Hot" coil is grounded through Engine Coolant Temperature (ECT) sender. Resistance of the ECT sender is high when coolant is cold and resistance is low when coolant is hot.

CRUISE INDICATOR

The CRUISE indicator illuminates when cruise control system is turned on and system is active (controlling vehicle speed).

FASTEN SAFETY BELTS INDICATOR

The FASTEN SAFETY BELTS indicator illuminates when ignition switch is in RUN position, with either front door open and/or front safety belts not fastened. The chime module will sound when ignition switch is turned to RUN position, with the driver's safety belt not fastened. The chiming will stop after 6-8 seconds, or as soon as driver's safety belt is fastened, whichever occurs first. The FASTEN SAFETY BELTS indicator will turn off within 60-90 seconds, or as soon as the driver's safety belt is fastened, whichever occurs first.

LOW COOLANT INDICATOR

On vehicles with a low coolant switch in the coolant surge tank, the LOW COOLANT indicator illuminates if coolant level in surge tank is low. Light will remain illuminated until ignition is turned off, or coolant level in surge tank is restored to normal level.

FUEL GAUGE

Circuit consists of an electrically-operated indicator in IPC and a fuel tank pick-up/sending unit. Gauge indicates quantity of fuel in tank when ignition switch is in RUN position. When ignition switch is in the OFF, START, LOCK or ACC position, pointer may come to rest at any position. A sending unit in the fuel tank changes resistance with fuel level. Resistance range of sending unit is approximately zero (tank is empty) to 90 ohms (tank is full).

OIL PRESSURE INDICATOR

Oil pressure indicator is controlled by a pressure-operated switch located on engine block. When ignition switch is turned to the RUN or START position, indicator should illuminate as a bulb test. After engine is started, oil pressure indicator should turn off when correct oil pressure is reached.

OIL PRESSURE GAUGE

Gauge indicates engine oil pressure when ignition switch is in RUN position. Pointer is moved by 2 magnetic coils which pull on pointer in opposite directions. One coil is grounded through fuel pump/oil pressure switch/sender which varies its resistance in relation to engine oil pressure. When oil pressure is low, resistance is low, and when oil pressure is high (about 80 psi), resistance is high (about 90 ohms).

SERVICE ENGINE SOON INDICATOR

SERVICE ENGINE SOON indicator, mounted in IPC, illuminates during engine starting and remains illuminated a short time after engine is started. If indicator illuminates while driving, the Engine Control Module (ECM) or emission control system may require service. The indicator is controlled by ECM.

VOLTS INDICATOR

The VOLTS indicator illuminates when ignition switch is in the RUN position and engine is not running. The VOLTS indicator also illuminates when engine is running and when an under- or overvoltage condition exists.

VOLTMETER

With ignition switch in RUN position and engine off, voltmeter should indicate battery voltage. With engine running, voltmeter indicates charging system voltage.

TAILGATE AJAR INDICATOR

Some models are equipped with an indicator on dash that illuminates when tailgate is ajar and ignition switch is in RUN position. Switch at tailgate supplies a ground to circuit when tailgate is ajar.

AIR BAG PRECAUTIONS

Observe the following precautions when working on vehicles equipped with Supplemental Inflatable Restraint (SIR) air bag systems

1. Before performing any instrument panel testing, diagnosis or repair, disable SIR system by disconnecting negative battery cable and Yellow 2-pin connector at base of steering column.
2. Wait 20 MINUTES before making SIR repairs. SIR system retains enough voltage, for a short time after disconnecting power, to deploy air bag.
3. To avoid accidental air bag deployment, avoid SIR wiring harness when trouble shooting instrument panel components. All SIR wires are color-coded Yellow.

TESTING

Note. For speedometer testing, see appropriate G - TEST W/CODES article in ENGINE PERFORMANCE.

INSTRUMENT PANEL CLUSTER (IPC) CONNECTOR PIN IDENTIFICATION

See appropriate table to identify IPC connector pins and circuits. (Scheme 1)

IPC CONNECTOR C1 CIRCUIT IDENTIFICATION

IPC CONNECTOR C2 CIRCUIT IDENTIFICATION

Scheme 1

ALTERNATOR INDICATOR TEST

1. If charge indicator is on all the time, go to next step. If charge indicator is inoperative, disconnect alternator connector. Connect 15-amp fused jumper wire between alternator connector terminal "L" (Brown wire) and ground. Turn ignition on. If charge indicator comes on, check for poor connection at alternator terminal "L". If connection is okay, replace alternator. If charge indicator does not come on, check bulb, Pink wire, and Brown wire for an open circuit. If wires are okay, replace IPC.
2. If charge indicator is on all the time, disconnect alternator connector. Turn ignition on. If charge indicator does not come on, replace alternator. If charge indicator comes on, check Brown wire and IPC printed circuit for a short to ground. If circuit is okay, replace IPC.

Indicator Diagnosis

1. Battery voltage is applied to BRAKE indicator when ignition switch is in RUN, BULB TEST or START position. Ground for circuit is supplied through any of several switches which monitor low brake fluid level, unequal brake pressure and parking brake lever engagement.
2. BRAKE indicator may also come on when a problem is detected in anti-lock brake system (if equipped). If there is a problem with BRAKE indicator functioning, check appropriate switches and circuits. See «WIRING DIAGRAMS»(/buick/century/v-1982-1996/remont/gauges-instrument-panels/#instrument-panel-analog) .

FUEL GAUGE READS INACCURATE TEST

1. Disconnect fuel gauge sender connector. Turn ignition switch to RUN position. Clip one lead of Fuel Gauge Tester (J-33431) to Purple wire of fuel sender connector. Clip remaining lead to Black/White, Black/Yellow or Black wire of fuel sender connector.
2. Set resistance dials of tester first to zero ohms, then set to 90 ohms. Gauge pointer should indicate empty, then full, respectively. If gauge responds as specified, replace fuel gauge sender. If gauge does not respond as specified, check Purple and Black/Yellow, Black/White or Black wire for high resistance. Also check printed circuit for high resistance.
3. If high resistance is present, repair or replace wires or circuit board as necessary. If high resistance is not present, check fuel gauge connections. If fuel gauge connections are okay, replace IPC. If connections are not okay, repair as necessary.

FUEL GAUGE ALWAYS READS EMPTY TEST

1. Disconnect fuel gauge sender connector. Turn ignition switch to RUN position. If gauge indicates full, repair or replace fuel gauge sender. If gauge does not indicate full, disconnect IPC connector.
2. Connect test light between IPC connector terminals C7 (Purple wire) and D10 (Pink wire). If test light does not light, repair IPC. If test light lights, repair short to ground in Purple wire.

FUEL GAUGE ALWAYS READS FULL TEST

1. Disconnect fuel gauge sender connector. Connect test light between battery voltage and Black or Black/White wire terminal of fuel gauge sender connector.
2. If test light does not illuminate, check for poor connection of Black or Black/White wire between fuel gauge sender unit and ground, or for open in Black or Black/White wire. If test light illuminates, connect a fused jumper wire between Purple wire terminal of fuel gauge sender connector and ground. Check fuel gauge.
3. If gauge indicates full, check Purple wire for open or poor connection between IPC and fuel gauge sender and printed circuit board. If Purple wire, connections, and printed circuit board are okay, repair IPC. If gauge indicates empty, check for poor connection at fuel gauge sender connector Purple wire terminal. If connection is okay, replace fuel gauge sender.

COOLANT TEMPERATURE GAUGE TEST

1. Turn ignition switch to RUN position. If coolant temperature gauge indicates high coolant temperature with coolant temperature low, go to step 4). If coolant temperature gauge does not indicate high coolant temperature with coolant temperature low, disconnect coolant temperature sensor connector.
2. Using voltmeter, check voltage between coolant temperature sensor connector terminal "C" (Dark Green wire) on 2.2L or terminal "B" (Dark Green wire) on 3.1L, and ground. If battery voltage is present, check for poor connection at coolant temperature sensor. If connection is okay, replace coolant temperature sensor.
3. If battery voltage is not present, check for poor connection at instrument cluster connector C2 terminal No. 10 (Dark Green wire) or for open circuit. If connection and Dark Green wire are okay, replace gauge.
4. Disconnect coolant temperature sensor connector. If coolant temperature gauge does not indicate low coolant temperature, check for short to ground in Dark Green wire. Also check instrument cluster printed circuit board. If Dark Green wire and printed circuit board are okay, replace gauge. If coolant temperature gauge indicates low coolant temperature, replace coolant temperature sensor. COOLANT TEMPERATURE GAUGE RESISTANCE SPECIFICATIONS Application Gauge Indication Century 55 Ohms (1) Hot 1500 Ohms (1) Cold (1) Resistance setting on Tester (J-33431).
5. If gauge responds correctly, replace coolant temperature sender. If gauge does not respond as described, check Dark Green/White wire for open or high resistance. If circuit is okay, replace IPC. See «INSTRUMENT PANEL CLUSTER (IPC) R & I»(/buick/century/v-1982-1996/remont/gauges-instrument-panels/#instrument-panel-analog) under REMOVAL & INSTALLATION.
6. Disconnect coolant temperature sender. Ground Dark Green/White wire at coolant temperature sender connector. If coolant gauge reads HOT, replace coolant temperature sender.
7. If coolant gauge does not read HOT, check Dark Green/White wire for open. If circuit is okay, replace IPC. See «INSTRUMENT PANEL CLUSTER (IPC) R & I»(/buick/century/v-1982-1996/remont/gauges-instrument-panels/#instrument-panel-analog) under REMOVAL & INSTALLATION.

TAILGATE AJAR INDICATOR TEST

1. If indicator does not turn on when tailgate is open, go to step 2). If indicator stays on with tailgate closed, turn ignition switch to RUN position and disconnect tailgate ajar switch. If indicator turns off, replace tailgate ajar switch. If indicator remains illuminated, check Dark Green wire for short to ground.
2. Turn ignition switch to RUN position. Disconnect tailgate ajar switch connector. Connect jumper wire between Dark Green wire and ground. If indicator illuminates, replace tailgate ajar switch. If indicator does not illuminate, check for bad indicator bulb or Dark Green wire for open.

HEADLIGHT SWITCH

With headlights off, no voltage should be present at headlight switch terminal "D" (Yellow wire). With headlights on, battery voltage should be present at headlight switch terminal "D" (Yellow wire).

REMOVAL & INSTALLATION

1. Disconnect negative battery cable and isolate. Remove left trim plate. Remove shift indicator clip from steering column shift bowl. Remove 4 cluster attaching screws. On vehicles with column shift, shift transaxle to "1" position.
2. Place a clean shop towel over column to prevent scratching steering column. On models with tilt wheel, lower steering wheel as far as possible and unscrew tilt lever. On all models, tip top of IPC down and work IPC out of instrument panel. Disconnect electrical connectors. To install, reverse removal procedure.

Instrument Panel Wiring Diagram. Scheme 2

See also:
• COMPUTER RELEARN PROCEDURES
• WIRING DIAGRAMS