AEM 30-4100 Digital Wideband UEGO Gauge User Manual

Installation Instructions for

30-4100

Gauge-Type UEGO Controller

WARNING:
This installation is not for the electrically or mechanically
challenged! Use this sensor with EXTREME caution! If you are
uncomfortable with anything about this, please refer the
installation to an AEM trained tuning shop or call 800-423-0046
for technical assistance. You should also visit the AEM

,!

This product is legal in California for racing vehicles only and should

AEM Gauge-Type UEGO Controller Parts

1 x UEGO Gauge Assembly
1 x UEGO Sensor
1 x O2 Sensor Bung
4 x Butt Connectors
1 x Installation Instruction

Replacement O2 Sensor Components

30-2001 UEGO Sensor
35-4005 Mild Steel Oxygen Sensor Bung (welding required)

Performance Electronics Forum at http://www.aempower.com

NOTE: AEM holds no responsibility for any engine damage that
results from the misuse of this product!

never be used on public highways.

ADVANCED ENGINE MANAGEMENT INC.

th

2205 126

Phone: [phone] Fax: [phone]

© 2004 Advanced Engine Management, Inc.

Street Unit A, Hawthorne, CA. 90250

http://www.aempower.com

Instruction Part Number: 10-4000 Rev 4

Page 1

Congratulations! The 52mm (2-1/16”) AEM Universal Exhaust Gas Oxygen (UEGO)
Gauge features a digital readout and sweeping 24 color-coded light emitting diode
(LED) display, providing immediate reference to the engine air fuel ratio (or lambda) in
real-time. The AEM gauge is ideal for all vehicles including carbureted applications and
engine dynamometers. A user-programmable 0-5V analog output is included and can
be used with data loggers as well as most Electronic Fuel Injection (EFI) systems
including the AEM Engine Management System (EMS). A serial data stream is also
integrated for air fuel (or lambda) ratio output to a RS-232 com port.

Because the AEM gauge utilizes the internal AEM UEGO controller and Bosch UEGO
Sensor, it is accurate and repeatable to 0.1 of an air/fuel ratio point! With this, there is
no abrupt oscillation as found in many competitor gauges, which utilize a narrow band
oxygen sensor detecting only stoichiometry.

Typical production vehicle oxygen sensors rely on “Nernst Cell” technology, commonly
called “Narrow Band” and sometimes erroneously described as “Wide Band”. This is a
very cost effective method that outputs a voltage based on the oxygen content of the
gas being sampled. It is accurate in the region surrounding stoichiometric operation and
leaner. Unfortunately, in the rich region where high performance engines usually
operate, their accuracy and repeatability is virtually non-existent.

Characteristic curve of a Nernst Cell O2 Sensor

The rich region output of narrow band O2 sensors is temperature dependant, which
renders it useless if an accuracy better than 1.5:1 AFR is desired. This is immediately
obvious given the fact that a single output voltage actually represents wildly different air
fuel ratios depending on the unregulated and unmeasured sensor temperature. These
sensors were designed for operating closed loop around stoichiometry (14.64:1 for
gasoline), and for performance tuning they are useless.

The heart of the AEM gauge is the Bosch LSU4.2 Universal Exhaust Gas Oxygen
(UEGO) sensor. This type of sensor is commonly referred to as “laboratory grade” and
works on a different principle than the narrow band oxygen sensor found in most

Page 2

vehicles. Its unique design makes precision AFR measurements possible over the
entire operating range.

UEGO sensors use a “current pump” to determine the actual oxygen concentration
within the sensing element or. The output is in the form of a very small current, which
varies depending on the air-fuel ratio. This is completely different from a narrow band
oxygen sensor, which directly outputs a voltage. The UEGO sensor design allows
measurement of the exact air fuel ratio over the entire operating range.

Each AEM UEGO sensor is individually calibrated and a resistor integral at the
connector body is laser trimmed with this value. This process replaces the traditional
“free air” calibration procedure when changing sensors and implements a sensor
specific calibration for unparalleled accuracy.

UEGO Sensor laser etched calibration resistor

INSTALLATION

Disconnect the negative (-) battery cable. There are four flying leads from the AEM
UEGO Gauge. Connection for two of the wires is mandatory and optional for the other
two, as shown below.

BOSCH LSU4.2 UEGO Sensor

UEGO

Gauge &

RED:

BLACK:

WHITE:

12V Power

Chassis Ground

0-5V Output

Controller

BLUE:

Serial Output

Page 3