Computer problem
2003 Chevy Cavalier 4 cyl Front Wheel Drive Automatic 111000 miles
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The diagnostic test at Auto Zone said the IAT was not working. So I replaced it and reset the computer. It works fine when the engine is cold and after it's been reset. As soon as the car warms up the engine light comes back on, the idle is low, transmission starts knocking when you take off like a motor mount is out, but it isn't. What could be causing this problem?

Is the IAT causing the light to come on again? Can you have the codes read again and post the code here?

The light doesn't come back on immediately. Once the engine warms up you can feel roughness in it and the idle drops and then the light will come back on. Then it will knock again like the motor mount is out.

I live 20 miles from the closest town, to put it back on the tester I will have to drive into town and do it. I will do this later this afternoon.

THANK YOU very much for your prompt response!

You might want to buy a hand held scanner for it, they range in price from basic at around 40.00 to several thousnad dollars...save you the trip next time and they work on all cars and light trucks sold in the USA from 96 to present.

Thank you for the info about the scanner. I'm not sure that I will even be keeping this pos so I won't be getting the scanner...well...not today anyway...LOL

I did get the code though...it is "P0113".

Also, I noticed after resetting again that my son sat in the car and shifted back and forth, while I was underneath the car. At first it was very smooth, however, the engine would move back and forth a little more than normal. Then all of a sudden you could tell that, what seemed like anyway, the IAT sensor, screwed up again because it klunked very hard, harder than what it normally does, then the car died instantly. I started it back up, it was rough again and now it appears the motor mount (long bar on passenger side) is out. Could this be causing a knock sensor or something of the sort to kick in?

P.S. This is the only code that read with the scanner at Auto Zone! When I referred to the computer and IAT being reset in my earlier post, I meant that it is staying close to 1000rpm's and when you turn on the air conditioner the RPM's go up just a hair. When the light comes back on RPM's drop to about 500 and the air conditioner doesn't affect the RPM's.

SELF-DIAGNOSTICS -2003 Chevrolet Cavalier
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NOTE: For circuit reference, see WIRING DIAGRAMS. For component locations, see COMPONENT LOCATIONS. For connector identification, see CONNECTOR IDENTIFICATION.

DTC P0113: INTAKE AIR TEMPERATURE SENSOR CIRCUIT - HIGH VOLTAGE
Description
The Intake Air Temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an excessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets.
Conditions For Running DTC
 DTCs P0117, P0118, P0125, P0502 or P0503 are not set.
 The engine run time is more than 5 minutes.
 The Vehicle Speed Sensor (VSS) indicates that vehicle speed is less than 15 MPH.

Conditions For Setting DTC
The IAT sensor signal voltage indicates that the intake air temperature is less than -38°F (-39°C) for 6.25 seconds.

Actions Taken When DTC Sets
 The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
 The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions For Clearing MIL/DTC
 The PCM turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
 A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
 A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

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SELF-DIAGNOSTICS -2003 Chevrolet Cavalier
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 Clear the MIL and DTC using a scan tool.
Test Description
The number below refer to the step number on the diagnostic procedure.
6 - This step 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.

Diagnostic Procedures
1.Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step. 2.Connect scan tool. Turn ignition switch to RUN position, with engine off. Observe the IAT sensor parameter. Is the IAT sensor temperature less than -36°F (-38°C)? If yes, go to step 4. If no, go to next step. 3.Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC reset? If yes, go to next step. If no, go to DIAGNOSTIC AIDS. 4.Turn ignition switch to OFF position. Disconnect IAT sensor harness connector. Connect a Digital Multimeter (DMM) between the signal circuit of the IAT sensor and a good ground. Turn ignition switch to RUN position. Does the DMM voltage measure more than 5.2 volts? If yes, go to next step. If no, go to step 6.

NOTE: If a short to voltage occurs the Engine Coolant Temperature (ECT) sensor may be damaged.
5.Check the signal circuit for a short to voltage. Repair as necessary. Did you find and correct the condition? If yes, go to step 15. If no, go to 12. 6.Turn ignition switch to OFF position. Disconnect IAT sensor harness connector. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and the low reference circuit at the IAT sensor harness connector. Turn ignition switch to RUN position, engine off. Observe the IAT sensor temperature using a scan tool. Is the IAT sensor temperature more than 262°F (128°C)? If yes, go to step 10. If no, go to next step. 7.Turn ignition switch to OFF position. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor harness connector and a known-good ground. Turn ignition switch to RUN position, engine off. Observe the IAT sensor temperature using a scan tool. Is the IAT sensor temperature more than 262°F (128°C)? If yes, go to step 9. If no, go to next step. 8.Check the signal circuit of the IAT sensor for an open circuit or high resistance. Did you find and correct the condition? If yes, go to step 15. If no, go to step 12. 9.Check the IAT sensor low reference circuit for high resistance or an open. Did you find and correct the condition? If yes, go to step 15. If no, go to step 12. 10.Check the IAT signal circuit for a short to any 5-volt reference circuit. Did you find and correct
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SELF-DIAGNOSTICS -2003 Chevrolet Cavalier
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the condition? If yes, go to step 15. If no, go to next step.
NOTE: The sensor may be damaged if the circuit is shorted to a voltage source.
11.Check for an intermittent and for a poor connection at the IAT sensor. Repair as necessary. Did you find and correct the condition? If yes, go to step 15. If no, go to step 13. 12.Check for an intermittent and for a poor connection at the PCM. Repair as necessary. Did you find and correct the condition? If yes, go to step 15. If no, go to step 14. 13.Replace the IAT sensor. After repair, go to step 15. 14.Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE REPROGRAMMING under PROGRAMMING. After replacing PCM, go to next step. 15.Clear the DTCs using a scan tool. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC run and pass? If yes, go to next step. If no, go to 2. 16.Observe the CAPTURE INFO using a scan tool. Are there any DTCs that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS. If no, system is okay at this time.
Diagnostic Aids
 When the vehicle is at ambient temperature the IAT sensor and ECT sensor temperatures should be relatively close to each other. See TEMPERATURE VS. RESISTANCE table.
 If a short to a separate 5-volt source occurs this DTC may set. If this condition exists, a continuity test to all other PCM 5-volt reference circuits will be necessary.
 If an intermittent condition is suspected, refer to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.

© 2007 Mitchell Repair Information Co., LLC.

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