TM 5-3805-291-23-1
ELECTRICAL SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
0013 00
ENGINE SPEED/TIMING SENSOR CIRCUIT TEST
0013 00
N OT E
Use this procedure to troubleshoot any suspectproblems with crankshaft (primary) speed/timing
sensor or with camshaft (secondary) speed/timing sensor.
This procedure covers folowing diagnostic codes:
l
a.
320-02 Speed/Timing Sensor Loss of Signal
b.
320-11 Speed/Timing Sensor mechanical failure
c.
342-02 Loss of Secondary Engine Speed signal
d.
342-11 Secondary Engine Speed Sensor mechanical failure
Engine uses two engine speed/timing sensors. Secondary engine speed/timing sensor monitors
camshaft gear and primary engine speed/timing sensor monitors crankshaft gear.
Both engine speed/timing sensors detect referencefor engine speed and timing from a unique pat-
tern on respective gear.
ECM counts time between pulses created bysensor as gear rotates to determine rpm.
Under normal operation, s condary engine speed/timing sensor is used to determine timing for
e
starting purposes.
Secondary engine speed/timing sensor is used to determine whenpiston in No. 1 cylinder is at top
of compression stroke.
When timing has been established, primary enginespeed/timing sensor is then used to determine
engine speed and signal from secondary camshaft sensor is ignored.
After locating No. 1 cylinder, EC triggers each injector in correct firing order and at correct
M
fuel injector timing.
Actual timing and duration of eachinjection is based on engine rpm and load. If engine is running
and signal from primary engine speed/timing sensor is lost, a slight change in engine performance
will be noticed when ECM performs changeover to secondary engine speed/timing sensor. Loss of
signal from secondary engine speed/timing sensor during engine operation will not result in any
noticeable change in engine performance. However, if signal from secondary engine speed/timing
sensor is not present during start-up following conditions may exist:
a.
Engine may require a slightly longer period of time to startup.
b.
Engine may run rough for a few seconds until ECM determines proper firing order by using
primary engine speed/timing sensor only.
Engine will start andrun when only one sensor signal is present from either sensor.
Loss of signal from both sensors during engineoperation will result in termination of injection
and shutting down of engine by ECM.
Loss of signal from both sensors duringstart-up will prevent engine from starting.
Both sensors are magnetic sensors with an inte ral connector. Sensors are not interchangeable.
g
Do not switch positions of sensor. If sensors are replaced, a timing calibration is not necessary for
engine.
When sensors are being installed, complete all of following tasks:
a.
Lubricate O-ring with oil.
b.
Ensure sensor is fully seated into engine before tightening bracket bolt.
c.
Ensure connector is properly latched.
d.
Ensure harness is properly secured, and ensure tiedown straps are placed in correct location.
