IK0800284 - Ambient Air Temperature (AAT) senor faults

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CANADA, UNITED STATES, MEXICO Document ID: IK0800284

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Major System:

ELECTRICAL SYSTEM

Created:

5/16/2011

Current Language: English

Last Modified: 10/15/2013

Other Languages : Français, Español,

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Will (Mark) Wiley

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Title: Ambient Air Temperature (AAT) senor faults
Applies To: 2010 EPA MaxxForce® 11 and 13 ProStar® and WorkStar®

DESCRIPTION
There are two ambient temperature sensors. The sensor located behind the cab along the left frame rail is the sensor the engine uses. There is
also a sensor located at the front of the chassis that the gauge cluster uses for the temp display. This article discusses the Engine
AAT Sensor first. Information on the Cab AAT can be found at the bottom of this article.

POSSIBLE DIAGNOSTIC TROUBLE CODES
SPN
171
171
171

FMI
4
3
2

MODULE
Engine
Engine
Engine

DESCRIPTION
AAT signal out of range LOW (Body mounted sensor)
AAT signal out of range HIGH (Body mounted sensor)
AAT signal does not agree with other sensors

NOTE: If the ECM is setting/logging code 171 2 and the sensor tests good do NOT replace the sensor, there is a new calibration coming in
December 2013 to address this issue.

LOCATION
The Engine sensor is located on the left frame rail midway between the back of cab and front drive axle, or near the front drive axle. The two
photos below show both possible mounting locations.

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IK0800284 - Ambient Air Temperature (AAT) senor faults

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ENGINE CIRCUIT DIAGRAM

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IK0800284 - Ambient Air Temperature (AAT) senor faults

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CAB AMBIENT TEMPERATURE SENSOR
The instrument cluster, connector 1501 pin 9, sends a 5-volt source to the temperature sensor. As the voltage goes across the temperature
sensor it decreases, the amount of voltage drop depends on outside temperature. The reduced voltage then returns to the instrument cluster on
pin 8 of connector 1500. The instrument cluster turns the received signal into to the temperature shown on the display.

CAB SENSOR TROUBLESHOOTING
Note: The Electronic Gage Cluster display will replace temperature reading with two dashes (- -) if a fault is present with the Ambient Temperature
Sensor circuit.

Step

Test Points

Specification

In Spec

NOT In Spec

1

Measure voltage between ambient temperature sensor
connector cavity A and GND

5 +/- 0.5 Vdc

Go to
next step

Inspect wire from cluster 1501-9 to AAT
sensor pin A for open or short

2

Measure voltage between ambient temperature sensor
connecotr cavity A and cavity B

5 +/- 0.5 Vdc

Go to
next step

Inspect ZVR wire from cluster 1500-8 to
AAT sensor pin B for open or short

Actual Ambient Temperature

Resistance value for sensor

50˚C (122˚F)

3557.7 - 3648.2 Ω OHMS

25˚C (77˚F)

9862.5 - 10137.5 Ω OHMS

0˚C (32˚F)

32197 - 33111 Ω OHMS

CAB CIRCUIT DIAGRAMS
IMPORTANT: Due to variations during vehicle production, be sure to select the most current wiring schematic manual, specific to the year and model of the
vehicle being serviced.



ProStar / LoneStar wiring for Cab Sensor
ProStar / LoneStar wiring for Cab Sensor with Front Axle Load Sensor

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IK0800284 - Ambient Air Temperature (AAT) senor faults





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HPV wiring for Cab Sensor
HPV wiring for Cab Sensor with Front Axle Load Sensor
TerraStar wiring for Cab Sensor

The Cab Temperature Sensor is typically mounted near the front bumper or on the cooling package. If the sensor cannot be found verify the
wiring to the gauge cluster is present.

OTHER RESOURCES



2006-2009 Cummins Ambient Air Temperature Sensor Location
2006-2009 Cummins Active Fault 249 / 256 Ambient Air Temperature Sensor 1 Circuit

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