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Page 23/63 UltraGauge™ EM User Manual www.ultra-gauge.com
Distance with
Check Engine
Light on
Gauge name Range Units Abbreviation
Miles with CEL on 0 to 40,722 miles mi CEL
Kilometers w/CEL on 0 to 40,722 kilometers km CEL
Distance traveled since the Check Engine Light (CEL) illuminated.
Fuel Rail
Pressure
Gauge name Range Units Abbreviation
Fuel Rail PSI 0 to 95,050 PSI FR PSI
Fuel Rail 10kPa 0 to 65535 10kPa FR 10k
Fuel rail pressure at the engine relative to atmosphere (Gauge pressure), in Pounds per Square
Inch (PSI). This gauge supports much higher pressures.
Wide O
2
Sensor
Output lambda &
AFR
Gauge name Range Units Abbreviation
Wide O2 Bank1 Sensor 1 lambda
0 to 1.999 N/A
O2λ 1S1
Wide O2 Bank1 Sensor 2 lambda O2λ 1S2
Wide O2 Bank2 Sensor 1 lambda O2λ 2S1
Wide O2 Bank2 Sensor 2 lambda O2λ 2S2
Wide O2 Bank1 Sensor 1 lambda . O2λ 1S1
Wide O2 Bank1 Sensor 1 lambda . O2.λ 1S2
Wide O2 Bank2 Sensor 1 lambda . O2.λ 2S1
Wide O2 Bank2 Sensor 2 lambda . O2.λ 2S2
The ECM monitors the Wide band O2 sensor and outputs Lambda. Lambda is the measure of
the actual Air to Fuel ratio as compared to the ideal or Stoichiometric Air to Fuel ratio. It is a
ratio and has no units.
λ = Air
MASS
/Fuel
MASS
(Actual)
Air
MASS
/Fuel
MASS
(Stoichiometric)
λ = 1 = ideal mixture
λ > 1 = lean mixture
λ < 1 = rich mixture
See the AFR discussion at the end of this document
There are two possible sets of Lambda parameters returned by the ECM. One is current based
and the other voltage based. While there is only one set of sensors and it would seem that a
given vehicle would support either voltage or current, it is possible for the ECM to support
both. Current based lambda have a “.” in the description and abbreviation. The value from
both types should be identical.
EGR % Flow
Commanded
Gauge name Range Units Abbreviation
EGR % Flow Cmd 0 to 100 % EGR% flow
The percent of flow through the Exhaust Gas Recirculation (EGR) valve, where 0% is closed
and 100% is wide open. This is the commanded value indicating that the Engine Control
Module (ECM) is requesting the EGR to have the desired flow. The actual flow may be
different if there is an issue with the EGR.
EGR % Error
Gauge name Range Units Abbreviation
EGR % Error 0 to 100 % EGR %Err
Exhaust Gas Recirculation (EGR) valve error is a percent of commanded EGR
EGR Error = EGR (actual) – EGR (commanded) X 100
EGR (commanded)
For example, if 20% EGR flow is commanded and 15% is actually delivered, then EGR Error
is (15-20)/20 x 100 = -25%
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