AEM Digital Wideband UEGO Gauge 304100 User Manual

							ADVANCED ENGINE MANAGEMENT INC. 
2205 126th Street Unit A, Hawthorne, CA. 90250 
Phone: (310) 484-2322 Fax: (310) 484-0152 
http://www.aempower.com 
Instruction Part Number: 10-4000 Rev 4 
© 2004 Advanced Engine Management, Inc. 
 
 
Page 1 
 
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 
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!
 
This product is legal in California for racing vehicles only and should 
never be used on public highways. 
 
 
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) 
 
 
  
						

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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  
						

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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. 
 
12V Power
Chassis Ground
0-5V Output
Serial Output
BOSCH LSU4.2 UEGO Sensor
ControllerUEGO
Gauge &
RED:
BLACK:
WHITE:
BLUE:
  
						

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Gauge-Type UEGO Controller Installation 
 
 
RED   
Connect to a switched 10-18 volt power source utilizing a 10A fuse. 
 
BLACK   
Connect to a clean power ground. 
 
*WHITE  
Connects to any Stand Alone ECU unit that accepts a 0-5 volt input. 
 
*BLUE  
Connects to a RS-232 com port for hyper-terminal data logging. 
 
*optional (see below) 
 
 
Analog Output 
If the AEM UEGO gauge is to be connected to an AEM EMS, the UEGO gauge’s 
WHITE Analog Output wire shall be connected to an EMS Lambda input. Locating a 
suitable Lambda input channel can be done using the Application Notes provided with 
the EMS. If the Application Notes are not readily accessible, a current list of AEM 
Engine Management Systems is illustrated below.  
 
Lambda input channel locations of current EMS application list ( see EMS 
instructions for ECU connector pictures) 
 
AEM EMS P/N  Lambda #1 Pin  Lambda #2 Pin 
30-1000/1001/1002/1040 D14  D16 
30-1010/1012/1050/1052 C16  A23 
30-1020/1060 D7 D14 
30-1030/30-1070 C13 C14 
30-1100/1101 B47 B48 
30-1110 1C 9C 
30-1120/1121/1130 B6  B14 
30-1300 4 66 
30-1310/1311/1312/1313 76  75 
30-1400 29 43 
30-1401 44 43 
30-1510 C2-31 C2-33 
30-1600/1601/1602/1603 19  NA 
30-1610/1611/1612 46  52 
30-1620/1621/1622 29  55 
30-1710 2N 4J 
30-1720 C3 D3 
30-1800 C3 A2 
30-1810 D19 B17  
						

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Below is a list of AFR values that should be entered into the 02 Sensor #1(#2) Cal Table 
if inputting the analog signal to an AEM EMS. These calibration table(s) are found in the 
AEMPro software: Setup | Sensors | Oxygen Sensor | Oxygen Sensor #1(#2) 
 
When connecting to AEM’s EMS, make sure to verify that the O2 #1 Gain option is set 
so the voltage from the O2 #1 Volts parameter matches the voltage input at the EMS 
from the O2 sensor. An easy way to do this is to disconnect the UEGO sensor from the 
UEGO gauge. When in this state, the UEGO gauge will output 2.35 volts. You can then 
adjust the O2 #1 Gain until the O2 #1 Volts display in AEMPro reads 2.35 volts. 
 
02 Volts  Gasoline AFR Methanol AFR Propane AFR Ethanol AFR  CNG AFR 
0.00 10.00  4.42 10.72 6.14  9.90 
0.16 10.32  4.56  11.06 6.34 10.21 
0.31 10.62  4.69  11.38 6.52 10.51 
0.47 10.94  4.83  11.72 6.72 10.83 
0.62 11.24  4.96  12.05 6.91 11.12 
0.78 11.56  5.11  12.39 7.10 11.44 
0.94 11.88  5.25  12.73 7.30 11.76 
1.09 12.18  5.38  13.05 7.48 12.06 
1.25 12.50  5.52  13.40 7.68 12.37 
1.40 12.80  5.65  13.72 7.86 12.67 
1.56 13.12  5.79  14.06 8.06 12.99 
1.72 13.44  5.94  14.40 8.26 13.30 
1.87 13.74  6.07  14.72 8.44 13.60 
2.03 14.06  6.21  15.07 8.64 13.92 
2.18 14.36  6.34  15.39 8.82 14.21 
2.34 14.68  6.48  15.73 9.02 14.53 
2.50 15.00  6.62  16.08 9.22 14.85 
2.65 15.30  6.76  16.40 9.40 15.14 
2.81 15.62  6.90  16.74 9.60 15.46 
2.96 15.92  7.03  17.06 9.78 15.76 
3.12 16.24  7.17  17.40 9.98 16.07 
3.27 16.54  7.30  17.73 10.16 16.37 
3.43 16.86  7.45  18.07 10.36 16.69 
3.59 17.18  7.59  18.41 10.55 17.00 
3.74 17.48  7.72  18.73 10.74 17.30 
3.90 17.80  7.86  19.08 10.94 17.62 
4.05 18.10  7.99  19.40 11.12 17.91 
4.21 18.42  8.13  19.74 11.32 18.23 
4.37 18.74  8.28  20.08 11.51 18.55 
4.52 19.04  8.41  20.40 11.70 18.85 
4.68 19.36  8.55  20.75 11.89 19.16 
4.83 19.66  8.68  21.07 12.08 19.46 
4.99 19.98  8.82  21.41 12.27 19.78 
 
  
						

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Connecting to Stand alone ECU’s  
When connecting to a third party EFI system, the AEM UEGO gauge’s WHITE Analog 
Output wire shall be connected to the analog O2 sensor input of that system. Consult 
the documentation provided with the system for detailed instructions. (for AEM EMS see 
page 4) 
 
Serial Output (optional) 
The serial output can be used for data logging when an EFI system is not accessible. 
To run the data stream, a RS-232 (DB-9) Female Receptacle shall be purchased. 
 
12345
6789
 
Wire View of RS-232 (DB-9) Male Plug 
 
Two wires need to be connected to a RS-232 serial port. The BLUE wire from the AEM 
UEGO Gauge shall be connected to Pin #2 (RX) on the serial port for receiving data. 
Pin # 5 (GND) on the serial port shall be grounded. If a standard 9-pin serial cable is to 
be cut instead, the (RX) wire is typically RED and the (GND) wire is typically GREEN. 
However, this should be confirmed with a continuity tester before attempting. 
 
Use HyperTerminal for testing the data stream. This software is found on most PCs. To 
find HyperTerminal go to: Start | All Programs | Accessories | Communications | 
HyperTerminal. Name the New Connection and click OK. Set the COM port to the one 
being used and click OK.  
 
Bits Per Second = 9600 
Data Bits = 8 
Parity = None 
Stop Bits = 1 
Flow Control = Hardware 
 
Verify the settings above and click OK. When power is supplied to the AEM UEGO 
Gauge, AFR (or Lambda) data will be displayed, as shown below.  
  
						

							Page 7 
 
Data logging with HyperTerminal 
UEGO Sensor 
If attempting to route the UEGO Sensor through a tight space, AEM recommends 
temporally removing the light grey latch from the Bosch connector, as shown below. 
  
 
Gently pull the latch out away from the UEGO Sensor connector 
 
 
UEGO Sensor connector without latch 
 
If the UEGO sensor is to be put through a conduit or firewall, a 1.05in (26.7mm) drill is 
required. Refer to the two diagrams above when reassembling the connector. 
 
A weld-in M18 X 1.5 boss is supplied for sensor installation. Mount the O2 sensor in the 
exhaust system at least 18 inches downstream from the exhaust port. If you anticipate 
high EGTs (over 800C), run a turbocharger, run at high RPM for extended periods of  
						

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time or plan on running leaded race fuel then you must mount the sensor at least 36 
inches or more downstream of the exhaust port as all of these can cause the sensor to 
overheat. On turbocharged engines the UEGO sensor must be installed after the turbo 
charger, if not, the pressure differential will greatly effect the accuracy of the unit. For 
accurate readings, the sensor must be mounted before catalytic converters and/or 
auxiliary air pumps. To prevent collection of liquids between the sensor housing and 
sensor element during the cold start phase, the installation angle should be inclined at 
least 10° towards horizontal with the electrical connection upwards, see below.  
 
Minimum mounting angle for the UEGO Sensor 
Configuring Calibration Outputs 
If a different O2 sensor calibration is desired, the AEM calibration can be changed to 
one of three available. The AEM default position is (P0) if an AFR Gauge was 
purchased and (P1) if a Lambda Gauge was purchased. These settings implement a 
linear calibration with the most useful voltage range possible (0-5V). The AFR 
calibration (P2) is linear and similar to (P1) with a slightly smaller voltage range (1-2V). 
The AFR calibration (P3) emulates the Autronic Wideband O2 Sensor calibration (0-1V). 
The AFR calibration (P4) emulates a non-linear Nernst Cell calibration (0-1V). Refer to 
the Table and Graph for specific calibration details. 
 
To change the calibrations, a precision flat head screw diver is needed. Locate the 
small hole located on the back of the AEM gauge, as shown below. 
 
 
Calibration position screw location 
 
With the screw driver, clock the rotary switch into the desired calibration position, 
referring to the diagram below, and watch the alphanumeric readout, which will display 
the new position when entered.  
						

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P4
P3
P2
P1P0
ROTARY SWITCH
 
Calibration screw position settings 
 
The calibration will not be changed until the rotary switch reaches the middle of the new 
position. 
 
AEM Lambda Gauge Owners  
Because the Lambda gauge faceplate is calibrated for (
λ) and all other calibration 
positions are for AFR (Gasoline), AEM does not recommended changing the controller 
calibration, as instructed above. 
 
Below is the multiplier for calculating the Air Fuel Ratio (AFR) of common fuels from the 
Lambda value. 
 
Gasoline AFR   =   Lambda x 14.65 
Methanol AFR   =   Lambda x 6.47 
Propane AFR   =   Lambda x 15.7 
Ethanol AFR    =   Lambda x 9.00 
CNG AFR     =   Lambda x 14.5 
11.0 11.5
12.0
12.5 13.0 13.5
14.0
14.5
15.0
15.5
16.0
16.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
An a l o g  V o l t a g e  ( V )
Air/Fuel Gasoline (AFR)
0.75 0.80 0.85 0.90 0.95
1.00 1.05 1.10
Lambda (λ) 
AFR Small Volt Range (P2)AFR Autronic Em ul a tion (P 3)
AFR Ne rnst Em ula tion (P 4)AEM  GAUGE De fa ult (P 0 & P1) 
Calibration graph of available outputs  
						

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Specifications 
Gauge 
Supply Current (nominal): 1.3 amps 
0-5V Analog Outputs:  1 
Measuring Range:   0.751 to 1.143 Lambda 
Harness & Connector Temp Limit:  120C 
Sensor 
Type:  Bosch UEGO LSU4.2 
Accuracy: +/- 0.7% 
Exhaust Temp Limit:  1030C 
Cable & Protector Sleeve Temp Limit: 250C 
Connector Temp Limit:  120C 
Initial Warm-up Time:  Less than 20 seconds 
Weight: 80 grams 
Heater Current:  1.2A at 12.0V (each sensor) 
Mounting:  M18 X 1.5 thread, Torque to 30 ft-lbs 
Nominal Service Life: 
 
 
 80,000 km for Unleaded Fuel 
50,000 km for Leaded Fuel 0.15g Pb/l 
20,000 km for Leaded Fuel 0.40g Pb/l 
10,000 km for Leaded Fuel 0.60g Pb/l 
 
Notes 
The sensor contains a ceramic module and should not be subject to mechanical or 
thermal shock or it may be damaged. The sensor is not designed for operation on 
leaded fuels, doing so will dramatically shorten sensor life. Long term running in the rich 
region (Lambda < 0.95) will shorten sensor life. High exhaust temperatures (over 850C) 
will shorten sensor life. Engine oil consumption at a rate greater than 1 quart per 1,000 
miles will shorten sensor life. With the UEGO Sensor installed, do not run the engine 
without power applied to the gauge. 
 
12 MONTH LIMITED WARRANTY 
 
Advanced Engine Management Inc. warrants to the consumer that all AEM High Performance products will be free 
from defects in material and workmanship for a period of twelve (12) months from date of the original purchase. 
Products that fail within this 12-month warranty period will be repaired or replaced at AEM’s option, when 
determined by AEM that the product failed due to defects in material or workmanship. This warranty is limited to 
the repair or replacement of the AEM part. In no event shall this warranty exceed the original purchase price of the 
AEM part nor shall AEM be responsible for special, incidental or consequential damages or cost incurred due to the 
failure of this product. AEM does not warranty the UEGO sensor. Warranty claims to AEM must be transportation 
prepaid and accompanied with dated proof of purchase. This warranty applies only to the original purchaser of 
product and is non-transferable. All implied warranties shall be limited in duration to the said 12 month warranty 
period. Improper use or installation, accident, abuse, unauthorized repairs or alterations voids this warranty. AEM 
disclaims any liability for consequential damages due to breach of any written or implied warranty on all products 
manufactured by AEM. Warranty returns will only be accepted by AEM when accompanied by a valid Return 
Goods Authorization (RGA) number. Credit for defective products will be issued pending inspection. Product must 
be received by AEM within 30 days of the date the RGA is issued. 
 
Please note that before AEM can issue an RGA for a UEGO Gauge, it is first necessary for the installer or end user 
to contact the EMS tech line at 1-800-423-0046 to discuss the problem.  Most issues can be resolved over the phone.  
Under no circumstances should a system be returned or a RGA requested before the above process transpires.