Hummer H1 Service Manual page 846

Section 12 Electrical System
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Digital Ratio Adapter
Location
The digital ratio adapter is located under the center console on
the engine cover, just above the powertrain control module.
Removal
1. Remove the cup holder from the center console.
2. Disconnect the two harness connectors from the digital
ratio adapter.
Circuit Description
√
The speed sensor circuit consists of a magnetic induction type
sensor, a Digital Ratio Adapter (DRA) and wiring. Geared
teeth pressed on the output shaft induce an alternating current
in the sensor. This A/C signal is transmitted to the DRA. The
DRA compensates for various axle ratios and converts the sig-
nal into a digital signals for use by the speedometer, cruise
control, and the PCM. The DRA sends two different signal to
Approximate Reading
30 MPH
60 MPH
30 MPH
NOTE: The above table only applies to 2000 model year vehicles.
05745159
ENGINE
COVER
DIGITAL
RATIO
ADAPTER
POWERTRAIN
CONTROL
UNIT
01-S12-017
Figure 12-93.1 Digital Ratio Adapter Removal
Digital Ratio Adapter Out Put Signal to Speedometer
Electrical System
3. Pull the digital ratio adapter off of the hook and loop and
remove from the center console.
Installation
1. Install the digital ratio adapter in the center console on the
hook and loop.
2. Connect the harness connectors to the bottom of the digital
ratio adapter.
3. Install the cup holder in the center console.
the PCM. Circuit 565 sends a signal of 40 pulses per revolution
of the output shaft to the PCM. This signal is used to control
shift points, line pressure, TCC and diagnostic codes. Circuit
223 sends a signal of 4000 pulses per mile to the PCM. This
signal is used for cruise and DTCs. The DRA sends a separate
signal to the speedometer on circuit 353. This signal is a
128,000 pulse per mile signal.
Input
1066.6 Htz
2133.3 Htz
1066.6 Htz
12-74.1
Ascending Descending
X
X
X
3-1-01