Tachometer Inoperative/Improper (Analog)

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The tachometer gage in the IPC is driven directly from an output in the ignition module.

TEST DESCRIPTION

Test numbers refer to circled numbers on the diagnostic chart.

1. PCM data parameter PD11 Engine RPM and the displayed tachometer should be relatively close in readings across the displayable range.

2. Normal voltage readings at the IPC Tachometer input (Cavity "B1") are above 8 volts AC and will vary with changes in RPM.

3. Disconnecting the IPC and measuring the voltage eliminates the IPC from the circuit. If the voltage is still not above 8 volts AC, or does not vary with engine rpm, CKT 121 is suspect. If the voltage now reads correct, ensure no short or open conditions exist at the IPC connector. If good connection, the IPC must be drawing the circuit down.

NOTES ON INTERMITTENTS

Ensure god terminal contact at all electrical connection. Attempt to duplicate conditions under which failure was noted, while manipulating related wiring. If intermittent fluctuations occur, ensure proper routing of CKT 121.