B0521

CIRCUIT DESCRIPTION
The instrument panel cluster (IPC) receives engine RPM information from the powertrain control module (PCM). Engine RPM input information is obtained from the PCM on a dedicated engine speed input to the PC. The IPC also receives engine RPM data on the serial data line. The PCM is responsible for processing and sending engine RPM data to the IPC. The IPC will only display the engine RPM data that was sent by the PCM. The IPC monitors the engine RPM output information sent from the PCM for an out of range condition.

CONDITIONS FOR SETTING THE DTC
^ The IPC detects that the engine RPM is at least 7,400 RPM.
^ The above condition must be present for 1 second.

ACTION TAKEN WHEN THE DTC SETS
^ The IPC stores a DTC B0521.
^ The IPC displays engine RPM at 7,400 RPM.

CONDITIONS FOR CLEARING THE DTC
^ The IPC detects that the engine RPM is less than 7,400 RPM.
^ A history DTC clears after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ The code is cleared using on-board diagnostics.
^ The IPC receives a clear code command from the scan tool.

DIAGNOSTIC AIDS
^ The following conditions may cause an intermittent malfunction to occur:
- The PCM is unable to process the correct RPM data.
- Intermittent or erratic RPM signal sent from the PCM.
^ For intermittents and poor connections refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-6:

The number(s) below refer to the step number(s) on the diagnostic table.
2. Tests the tachometer operation. All tachometer malfunctions must be diagnosed and corrected first.