Spicer TPCS Troubleshooting Guide - Manual (Page 25)

22
Service Codes
Group: 3C! (Codes 18, 76,
77
)
Speed Signal (Codes 18, 76, 77)
This fault is set when ECU power has been cycled 50 times without sensing any speed input. Move vehicle at greater than 5 mph.
Did fault clear?
Determine type of speed sensor input:
Digital (TTL signal from engine ECU or speedometer)
Analog (pole sensor or VR type)
Data Link (SAE J1708/1587 or SAE J1939)
Sensor type?
Check adjustment on threaded
pencil speed sensor or drive tang on
mechanical speed sensor.
Use industry standard tools to verify
data link signal is OK.
Was a short found?
Check for opens:
Short speed sensor harness connector A
and B together.
Measure continuity between F2 and F3 on
ECU connector.
Was circuit open?
Replace speed sensor.
Repair as necessary.
Repair harness
as necessary.
Switch off ignition.
Disconnect speed sensor and ECU from harness.
Check for shorts on ECU connector:
- F2 to F3
- F2 to K2
- F3 to K2
Switch off ignition.
Disconnect speed input from signal
source and ECU from harness.
Check for shorts on ECU connector
F1 to K2.
Repair and verify speed signal source.
Check continuity of ECU
connector F1 to speed input.
Did active
code clear?
Replace ECU.
Note: ECUs are not a typical cause of problems. If an ECU
is replace, the system should be carefully rechecked to
make sure the problem has been fixed and does not reoccur.
Move vehicle at
greater than 5 mph.
Complete
Sensor problem?
Repair harness
as necessary.
Complete
Yes
Analog
Yes
No
No
Data Link
Yes
No
Yes
No
Yes
No
Digital