Test Step 2. Determine the Type of Vehicle Speed Problem

413

TM 9-2320-312-24-2

Troubleshooting Section

Result 2 The ET status screen and speed is stable,

Expected Result:

but incorrect.

All connectors, pins and sockets should be

Result 3 The ET status screen agrees with the

completely coupled and/or inserted and the harness

actual speed, but the ECM driven speedometer is

and wiring should be free of corrosion, abrasion

incorrect or inoperable.

or pinch points.

Result 4 The speed that is displayed on the ET

Results:

status screen is not present, unstable, or erratic.

OK Proceed to Test Step 2.

Results:

Not OK

Result 1 There is not a vehicle speed problem

Repair: Perform the following repair:

at this time. If a problem still exists, continue

troubleshooting until the condition is resolved.

Repair the connectors or wiring and/or replace

STOP.

the connectors or wiring. Ensure that all of the

Result 2 Proceed with vehicle speed calibration

seals are properly in place and ensure that the

connectors are completely coupled.

and adjustment.

Verify that the repair eliminates the problem.

Repair: Perform the following diagnostic

procedure:

STOP.

Troubleshooting, "Vehicle Speed Circuit -

Test Step 2. Determine the Type of

Calibrate"

Vehicle Speed Problem.

STOP.

A. Perform a dynamometer test on the vehicle or

Result 3 Proceed to Test Step 3.

perform a road test on the vehicle. Compare the

vehicle speed on the ET status screen against

Result 4 Proceed to Test Step 4.

the speedometer. Also, compare the vehicle

speed on the ET status screen against the actual

vehicle speed. The actual vehicle speed can

be measured on a dynamometer or the actual

vehicle speed can be measured by a stopwatch.

B. Monitor the vehicle speed status on ET while the

vehicle is parked and the engine is running.

C. Operate various electrical devices in the vehicle

while the vehicle speed is being monitored. In

order to operate the various electrical devices,

cycle the electrical devices to the ON position

and the OFF position.

D. Increase the engine rpm a few times and

decrease the engine rpm a few times.

Note: If the operation of a specific electrical

device is producing a vehicle speed problem, the

electrical device may be the source of an electrical

noise problem. An electrical noise problem is

also a possibility if increasing the engine rpm on

a stationary vehicle produces a vehicle speed

problem.

Expected Result:

Result 1 The speed that is displayed on the ET

status screen and the speed of the ECM driven

speedometer are stable and both speeds agree

with the actual speed.