
Page 29
VSL Protection
OEM
Description:
This tamper-resistant feature is a programmed engine
RPM limit that the engine will not exceed if the ECM
should lose the vehicle speed signal. In other words, if
the vehicle speed signal is lost the truck will not exceed
the Vehicle Speed Limit (VSL). The VSL Protection
parameter should be set high enough that the vehicle
can limp home, but low enough that it will not be capable
of exceeding the VSL.
Note: When VSL Protection is programmed to Top
Engine Limit (TEL) rpm, diagnostic codes 84-01, Loss of
Vehicle Speed Signal and 84-10, Vehicle Speed Rate of
Change are disabled.
Available:
All electronically controlled on-highway engines
covered in this handbook
Range:
Engine
Range
Cat DefaultMinimum Maximum
C-10, C-12,
C-15, C-16,
C11, C13, C15
1000 RPM TEL RPM TEL RPM
3126E GM 1700 RPM 1700 RPM 1700 RPM
3126E Other,
C7, C9
1700 RPM TEL RPM TEL RPM
Advantages:
The tamper resistance feature helps deter those who
may be tempted to try and circumvent the vehicle
speed signal. If the ECM were to lose the vehicle speed
signal for any reason, the engine rpm would be limited
to the programmed RPM value of the VSL Protection
parameter.
Disadvantages:
None
Recommendations:
✔ Caterpillar recommends electronic engines be
protected by setting this feature to an RPM value
equal to:
VSL Protection (rpm) =
VSL x R
a
x R
t
x M
60
where;
VSL = Vehicle Speed Limit
R
a
= Rear Axle Ratio
R
t
= Transmission Ratio in the highest gear
M = Tire revolutions per mile
Vehicle Speed Parameters