99-HVAC Code
Thread Starter
Racer
Joined: May 2009
Posts: 342
Likes: 1
From: Cutler Ohio
Ohio Events Coordinator
St. Jude Donor '09
99-HVAC Code
Been having some AC problems. Pulled codes and only found one (1) B0338, which according to my research is "Inside Air Temp Sensor Open".... Ok what does that mean and how would I fix, if it comes back? Cleared that along with a couple of others not pretaining to the HVAC. All codes were "H" not "C" so being history they may not come back.
I'm now leaning toward low feon as my AC problem. Any other or better ideas. I'm dealing with a "00" A4 Vert with Dual Zone HVAC. Thanks in advance, Randy"pear"Bauman
I'm now leaning toward low feon as my AC problem. Any other or better ideas. I'm dealing with a "00" A4 Vert with Dual Zone HVAC. Thanks in advance, Randy"pear"Bauman
Pro
Joined: Sep 2007
Posts: 735
Likes: 7
From: Bucks County Pa
Hi, The inside temp sensor defines the need for more or less cooling/heating in regards to the temp in the car. If it is bad or non operational, the system defaults to a 75 degree inside temp, and the system acts as though the inside car temp is 75. See below for replacement instructions. Now, you say you think you have low refrigerant, what makes you think that. What are the symptoms. You need to explain exactly what the system is doing , and we can help more. Such as, cold pass side, warm driv side or reversed, warm all vents, blower speeds not right, modes not performing properly, etc. What you have it set at and what the results are.
Good luck
Inside Air Temperature Sensor Replacement
Removal Procedure
Remove the center instrument panel accessory trim plate. Refer to Trim Plate Replacement - Instrument Panel (I/P) Accessory in Instrument Panel, Gages and Console.
Remove the driver knee bolster trim panel. Refer to Trim Panel Replacement - Knee Bolster in Instrument Panel, Gages and Console.
Carefully depress the sensor retaining tabs and remove the sensor from the driver knee bolster trim panel.
Installation Procedure
Align the inside air temperature sensor to the driver knee bolster trim panel, then push to secure the retaining tabs.
Important
The inside air temperature sensor must be aligned with and fit into the end of the inside air temperature sensor aspirator duct.
Be sure to ALIGN the inside air temperature sensor with the inside air temperature sensor aspirator duct, while installing the driver knee bolster trim panel.
Install the drivers knee bolster trim panel. Refer to Trim Panel Replacement - Knee Bolster in Instrument Panel, Gages and Console.
Install the I/P accessory trim plate. Refer to Trim Plate Replacement - Instrument Panel (I/P) Accessory in Instrument Panel, Gages and Console.
Good luck
Inside Air Temperature Sensor Replacement
Removal Procedure
Remove the center instrument panel accessory trim plate. Refer to Trim Plate Replacement - Instrument Panel (I/P) Accessory in Instrument Panel, Gages and Console.
Remove the driver knee bolster trim panel. Refer to Trim Panel Replacement - Knee Bolster in Instrument Panel, Gages and Console.
Carefully depress the sensor retaining tabs and remove the sensor from the driver knee bolster trim panel.
Installation Procedure
Align the inside air temperature sensor to the driver knee bolster trim panel, then push to secure the retaining tabs.
Important
The inside air temperature sensor must be aligned with and fit into the end of the inside air temperature sensor aspirator duct.
Be sure to ALIGN the inside air temperature sensor with the inside air temperature sensor aspirator duct, while installing the driver knee bolster trim panel.
Install the drivers knee bolster trim panel. Refer to Trim Panel Replacement - Knee Bolster in Instrument Panel, Gages and Console.
Install the I/P accessory trim plate. Refer to Trim Plate Replacement - Instrument Panel (I/P) Accessory in Instrument Panel, Gages and Console.
Thread Starter
Racer
Joined: May 2009
Posts: 342
Likes: 1
From: Cutler Ohio
Ohio Events Coordinator
St. Jude Donor '09
Thanks for the input so far!!
I'm leaning to Freon Level, based on the fact that from what I can tell everything is working properly (as I understand it should work). I'm not getting cooling from any one duct. When I switch between Defrost Dash Panel of Floor air seems to be properly directed. I have Temp setting between 65 and 75 with little or no change in felt temp. This "Senor Open" may cause this I assume, otherwise would it be a safe bet too think Freon Level?
This is the reason I come here is for the vast knowledge of the folks offering help. Thanks Again Randy"pear"Bauman
I'm leaning to Freon Level, based on the fact that from what I can tell everything is working properly (as I understand it should work). I'm not getting cooling from any one duct. When I switch between Defrost Dash Panel of Floor air seems to be properly directed. I have Temp setting between 65 and 75 with little or no change in felt temp. This "Senor Open" may cause this I assume, otherwise would it be a safe bet too think Freon Level?
This is the reason I come here is for the vast knowledge of the folks offering help. Thanks Again Randy"pear"Bauman
Pro
Joined: Sep 2007
Posts: 735
Likes: 7
From: Bucks County Pa
AC Temp Sensor.
Hi, if the inside temp sensor is bad, the temp dials will have no effect because the system defaults to a cabin temp of 75 degrees. Below is the diagnostics to determine if the sensor is bad.
If you are lucky, it may just be that a wire is loose, or a ground is loose on dirty. The sensors are not real expensive, so it may just be easier to replace it and see. That's old school mechanics, keep replacing until the thing runs right.
Good Luck
++++++++++++++++++++++++++++++++++
DTC B0338 Inside Air Temperature Sensor Open
Circuit Description
The inside air temperature sensor is located in the air outlet vent at the RH side of the steering column. In this position, it is exposed to the air that is present in the passenger compartment. This provides a sample of the inside air temperature to the sensor.
The sensor is a thermistor used to control the signal voltage at the HVAC Control Assembly. The HVAC Control Assembly supplies a reference voltage (about 5 volts internally) to the sensor and measures the voltage drop in the circuit to obtain a temperature signal. This signal is an input that tells the HVAC Control Assembly how much cooling or heating will be required for the passenger compartment. When the inside air temperature is cold, the thermistor resistance is high; therefore, the HVAC Control Assembly will receive a high signal voltage input. If the inside air temperature is hot, the thermistor resistance is low, the HVAC Control Assembly will receive a low signal voltage input.
Conditions for Setting the DTC
With the ignition in the ON position, CKT 734 is checked continuously.
CKT 734 stays at 4.5 volts or higher.
Action Taken When the DTC Sets
The system will use 24°C (75°F) as a default value.
The HVAC Control Assembly stores a DTC B0338 in memory.
Conditions for Clearing the DTC
Using the IPC clearing feature.
Using a scan tool.
A history DTC will clear after 50 consecutive ignition cycles if the conditions for the fault is no longer present.
Diagnostic Aids
If the DTC is a history or an intermittent. Try to perform the tests shown while "wiggling" wiring and connectors, this can often cause the malfunction to appear.
Visually inspect sensor connector and harness for damage, corrosion or water intrusion.
Check for adequate terminal tension, mis-routed harness, rubbed through wire insulation, and broken wire inside insulation.
The resistance value of the sensor must be close to the values given in the chart. If not the sensor is considered skewed and must be replaced.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
Tests for the proper operation of the circuit in the high voltage range.
Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
Step
Action
Value(s)
Yes
No
1
Did you perform the HVAC (CJ2) Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check
2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Inside Air Temp Sensor parameter in the HVAC data list.
Does the scan tool indicate that the Inside Air Temp Sensor parameter is within the specified range?
0.1-4.9 Volts
Go to Diagnostic Aids
Go to Step 3
3
Turn OFF the ignition.
Disconnect the Inside Air Temp Sensor.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Inside Air Temp Sensor parameter.
Does the scan tool indicate that the Inside Air Temp Sensor parameter is greater than the specified value?
4.9 Volts
Go to Step 4
Go to Step 5
4
Turn OFF the ignition.
Connect a 3 amp fused jumper wire between the signal circuit of the Inside Air Temp Sensor and the ground circuit of the Inside Air Temp Sensor.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Inside Air Temp Sensor parameter.
Does the scan tool indicate that the Inside Air Temp Sensor parameter is less than the specified value?
0.1 Volts
Go to Step 8
Go to Step 6
5
Test the signal circuit of the Inside Air Temp Sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 9
6
Test the signal circuit of the Inside Air Temp Sensor for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 7
7
Test the ground circuit of the Inside Air Temp Sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 9
8
Inspect for poor connections at the harness connector of the Inside Air Temp Sensor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 10
9
Inspect for poor connections at the harness connector of the HVAC Control Assembly. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 11
10
Replace the Inside Air Temp Sensor. Refer to Inside Air Temperature Sensor Replacement .
Did you complete the replacement?
--
Go to Step 12
--
11
Replace the HVAC Control Assembly. Refer to Control Assembly Replacement .
Did you complete the replacement?
--
Go to Step 12
--
12
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
--
Go to Step 2
System OK
If you are lucky, it may just be that a wire is loose, or a ground is loose on dirty. The sensors are not real expensive, so it may just be easier to replace it and see. That's old school mechanics, keep replacing until the thing runs right.
Good Luck
++++++++++++++++++++++++++++++++++
DTC B0338 Inside Air Temperature Sensor Open
Circuit Description
The inside air temperature sensor is located in the air outlet vent at the RH side of the steering column. In this position, it is exposed to the air that is present in the passenger compartment. This provides a sample of the inside air temperature to the sensor.
The sensor is a thermistor used to control the signal voltage at the HVAC Control Assembly. The HVAC Control Assembly supplies a reference voltage (about 5 volts internally) to the sensor and measures the voltage drop in the circuit to obtain a temperature signal. This signal is an input that tells the HVAC Control Assembly how much cooling or heating will be required for the passenger compartment. When the inside air temperature is cold, the thermistor resistance is high; therefore, the HVAC Control Assembly will receive a high signal voltage input. If the inside air temperature is hot, the thermistor resistance is low, the HVAC Control Assembly will receive a low signal voltage input.
Conditions for Setting the DTC
With the ignition in the ON position, CKT 734 is checked continuously.
CKT 734 stays at 4.5 volts or higher.
Action Taken When the DTC Sets
The system will use 24°C (75°F) as a default value.
The HVAC Control Assembly stores a DTC B0338 in memory.
Conditions for Clearing the DTC
Using the IPC clearing feature.
Using a scan tool.
A history DTC will clear after 50 consecutive ignition cycles if the conditions for the fault is no longer present.
Diagnostic Aids
If the DTC is a history or an intermittent. Try to perform the tests shown while "wiggling" wiring and connectors, this can often cause the malfunction to appear.
Visually inspect sensor connector and harness for damage, corrosion or water intrusion.
Check for adequate terminal tension, mis-routed harness, rubbed through wire insulation, and broken wire inside insulation.
The resistance value of the sensor must be close to the values given in the chart. If not the sensor is considered skewed and must be replaced.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
Tests for the proper operation of the circuit in the high voltage range.
Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
Step
Action
Value(s)
Yes
No
1
Did you perform the HVAC (CJ2) Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check
2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Inside Air Temp Sensor parameter in the HVAC data list.
Does the scan tool indicate that the Inside Air Temp Sensor parameter is within the specified range?
0.1-4.9 Volts
Go to Diagnostic Aids
Go to Step 3
3
Turn OFF the ignition.
Disconnect the Inside Air Temp Sensor.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Inside Air Temp Sensor parameter.
Does the scan tool indicate that the Inside Air Temp Sensor parameter is greater than the specified value?
4.9 Volts
Go to Step 4
Go to Step 5
4
Turn OFF the ignition.
Connect a 3 amp fused jumper wire between the signal circuit of the Inside Air Temp Sensor and the ground circuit of the Inside Air Temp Sensor.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Inside Air Temp Sensor parameter.
Does the scan tool indicate that the Inside Air Temp Sensor parameter is less than the specified value?
0.1 Volts
Go to Step 8
Go to Step 6
5
Test the signal circuit of the Inside Air Temp Sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 9
6
Test the signal circuit of the Inside Air Temp Sensor for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 7
7
Test the ground circuit of the Inside Air Temp Sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 9
8
Inspect for poor connections at the harness connector of the Inside Air Temp Sensor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 10
9
Inspect for poor connections at the harness connector of the HVAC Control Assembly. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 12
Go to Step 11
10
Replace the Inside Air Temp Sensor. Refer to Inside Air Temperature Sensor Replacement .
Did you complete the replacement?
--
Go to Step 12
--
11
Replace the HVAC Control Assembly. Refer to Control Assembly Replacement .
Did you complete the replacement?
--
Go to Step 12
--
12
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
--
Go to Step 2
System OK
Last edited by bestvettever; Aug 8, 2009 at 12:26 AM.
