Instrument Cluster Operation Without Electric Compass
Instrument Cluster
The instrument cluster is centered above the steering column in the instrument panel. The instrument cluster is removable from the rear of the panel (toward the steering wheel). The cluster contains instruments that provide the driver with information on vehicle performance.
The instrument cluster includes the following components:
| • | A speedometer (with integral odometer and trip odometer) |
| • | A tachometer (optional) |
| • | A boost gauge (Pontiac with U2F) |
| • | A fuel gauge |
| • | A volt gauge (Pontiac without U2F and Buick with UB3) |
| • | A coolant temperature gauge |
| • | An array of indicator lamps |
The vehicle speed reading on the speedometer is shown in both English (mph) and metric (km/h). The coolant temperature gauge omits any numerical readout markings and only contains a range of hash marks between C and H. The instrument cluster also contains numerous indicator lamps.
The instrument cluster assembly contains the cluster lens, and the speedometer/tachometer gauge module. The electric power is directed to each gauge through flexible printed circuits to each gauge module. The instrument cluster is serviceable as both a unit and as individual components (each gauge module may be removed from the cluster). The individual gauge modules are not to be disassembled.
When an instrument cluster is replaced, the law requires either the odometer reading of the replacement unit be set to register the original mileage or that a label be installed on the driver's door frame to show the previous odometer reading and the date of replacement. Since the mileage can NOT be set on the odometer in this vehicle, an odometer label must be used.
Instrument Cluster Service Precautions
Important: In testing for opens or shorts, do not ground or apply voltage to any of the instrument cluster circuits, unless you are instructed to do so by the diagnostic procedures.
The instrument cluster is designed in order to withstand normal current drains associated with vehicle operations. Avoid overloading any circuits. Only test these circuits using the J 39200 DMM. Refer to
Notice: Electrostatic discharge (ESD) can damage many solid-state electrical components.
ESD susceptible components may or may not be labeled with the ESD symbol. Handle
all electrical components carefully. Use the following precautions in order to avoid
ESD damage:
• Touch a metal ground point in order to remove your body's static charge
before servicing any electronic component; especially after sliding across the vehicle
seat. • Do not touch exposed terminals. Terminals may connect to circuits susceptible
the ESD damage. • Do not allow tools to contact exposed terminals when servicing connectors. • Do not remove components from their protective packaging until required
to do so. • Avoid the following actions unless required by the diagnostic procedure: - Jumpering or grounding of the components or connectors. - Connecting test equipment probes to components or connectors. Connect
the ground lead first when using test probes. • Ground the protective packaging of any component before opening. Do not
rest solid-state components on metal workbenches, or on top of TVs, radios, or other
electrical devices.
Diagnostic System
The instrument cluster is equipped with an extensive diagnostic system that is capable of performing the following functions:
| • | Detecting and compensating for malfunctions |
| • | Alerting the operator of a malfunction |
When a malfunction is detected, the instrument cluster performs one or both of the following actions:
| • | The instrument cluster displays warning messages. |
| • | The instrument cluster sets a diagnostic trouble code (DTC). |
Diagnostic Trouble Codes (DTCs)
The DTCs when set, indicate that the instrument cluster has detected a malfunction in a particular circuit or other system. The instrument cluster is programmed with routines for internal tests that the instrument cluster follows only under prescribed conditions (test conditions). When these conditions exist, the instrument cluster tests certain circuits or systems for a malfunction (failure conditions). When the failure conditions are true, a DTC is set current. Some DTCs command the instrument cluster to illuminate the SERVICE VEHICLE SOON indicator.
The DTCs are not stored in the instrument cluster's electrically erasable programmable read only memory (EEPROM). The DTCs are not retained after a battery disconnect.
Current DTCs
When the instrument cluster determines that the conditions for a DTC are present, the instrument cluster sets that DTC as current. All DTCs remain current until the next time the instrument cluster finds the conditions to set the DTC are no longer current. Some DTC's remain current after the conditions for setting it are no longer present until the next ignition cycle.
History DTCs
After the instrument cluster determines that the conditions for setting a DTC are no longer present it changes it to a history DTC. Some DTC's remain as current after the conditions for setting the DTC are no longer present until the next ignition cycle.
Instrument Cluster EEPROM
Important: The EEPROM is soldered into the instrument cluster. You can not service the EEPROM separately.
The instrument cluster contains a data storage device that can save critical data even when battery power is removed. This device is called the electrically erasable programmable read only memory (EEPROM). The EEPROM is used by the instrument cluster in order to store the following information:
| • | The odometer readings |
| • | The options settings |
| • | The manufacturing information |
Instrument Cluster Keep Alive Memory (KAM)
The instrument cluster contains a data storage area that saves pertinent data when the ignition is turned OFF. The data is lost when the battery power is removed. The data storage area is called the KAM. The instrument cluster uses the KAM in order to store the following information:
| • | The trip odometer readings |
| • | The fuel data information |
| • | The DTCs |
Dimming
The instrument cluster displays are dimmable. The indicators are non-dimmable. The instrument cluster backlighting (graphics and pointers) is directly controlled by the dash integration module (DIM) via the IP dimmer switch. The instrument cluster receives the dimming status via a class 2 message from the DIM.
