
Page 30
Tachometer Calibration
OEM
Description:
Programmed by the OEM, this parameter is used by the
ECM to convert the engine speed signal into revolutions
per minute for a tachometer.
Available:
All electronically controlled on-highway engines
covered in this handbook
Range:
Engine
Range
Cat
Default
Minimum Maximum
C-10, C-12, C-15, C-16,
C11, C13, C15
12.0 PPR 500.0 PPR 113.0 PPR
3126E GM, C7, C9
GM 530/540
2.0 PPR 500.0 PPR 17.5 PPR
C7, C9
GM T560
2.0 PPR 500.0 PPR 2.0 PPR
3126 Other &
2007 C7, C9, C13, C15
2.0 PPR 500.0 PPR 134.0 PPR
Advantages:
By using the ECM Output to drive the in-dash tachometer
the need for a separate sensor for the tachometer is
eliminated.
Recommendations:
✔ For most applications the factory default is correct.
✔ For ECM driven tachometer applications the in-
dash tachometer must be set to the same pulses
per revolution (PPR) setting as the ECM.
✔ To verify that the ECM is driving the tachometer,
perform the tachometer special test in Cat ET.
When running the special test, the tachometer
reading should sweep to approximately 1500 rpm.
If not, use the following calculation to correct the
Tachometer Calibration parameter value.
PPR
=
X
Tach 1500
PPR = current Tachometer Calibration value
Tach = value displayed on the tachometer during the
test
X = the desired Tachometer Calibration value
1500 = value that should be displayed on the
tachometer during the test
Vehicle Speed Parameters