Cadillac Owners Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
Hi All,

I´m very new to this forum, but have already enjoyed many of the post here. I´m the happy owner (after some difficulties) of a 1994/1997 mix of a Cadillac STS. After reading some very interesting posts here and some ´button fighting´ at the CCC, I managed to get a readout of DTC´s. The CCC in my car doesn´t have a ´WARMER´ button, nor does it have ´HI´ and ´LO´ buttons ;-)

Well I got the codes P0113 and P1111 which are Intake Air Temperature Sensor (Intermittent) High Voltage !!??? I was hoping for some bad connection or maybe a broken sensor that would be easy to replace. I have never been working on a N*, just an old Mustang 351, ´69, and I think they are a world apart. But the sensor High Voltage sounds more like some electronic device malfunctioning :confused:.

Could someone please explain to me what this means, or maybe point me to somewhere to find a description of what I can do about it. All this is of course started with the ´Service Engine Soon´ light to be on.

Sorry for a novice question,
 

·
Registered
Joined
·
1,121 Posts
PO113 **************************

Circuit Description
The Intake Air Temperature sensor is a thermistor, or variable resistor, that varies resistance based on temperature. Low temperature will result in a high signal voltage. DTC P0113 sets when the PCM sees an IAT sensor signal of -37°C (-35°F) or less with engine operating conditions that should have raised IAT temperature.

Conditions for Setting the DTC
Test Conditions
DTCs P0101, P0102, P0117, and P0118 not set.
Engine speed 500 RPM or greater for 20 seconds.
Vehicle speed has been greater than 7 MPH for 5 seconds this engine run cycle.
MAF input 60 grams per second or less.
Vehicle speed 50 MPH or less.
Engine coolant temperature 0°C (32°F) or greater.
OR

Engine coolant temperature less than 0°C (32°F) and IAT at least 27°C less than engine coolant temperature.

Failure Condition
The IAT sensor reading is -37°C (-35°F) or lower.

Action Taken When the DTC Sets
PCM turns ON the SERVICE EMISSION SYSTEM message.
PCM substitutes ambient air temperature for IAT.
Transaxle shift adapts are maintained at current levels.
The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.
Conditions for Clearing the MIL/DTC

The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.
Use a scan tool to clear DTCs.
Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.
Diagnostic Aids
IAT sensors can be damaged by backfire in the intake manifold. If the vehicle has had more than one IAT sensor replaced, check for signs of backfire. Under severe cold weather conditions this DTC could set if the actual outside temperature (IAT) is below -37°C (-35°F) and the ECT is at least 27°C warmer than IAT.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.

If IAT sensor circuit is open, IAT display should read -37°C (-35°F) or less.

Checking if PCM and wiring are functioning properly. Jumping the IAT Sensor Signal circuit to the IAT sensor ground circuit should cause IAT to read 147°C (247°F) or more.

Checking for poor terminal contact at IAT sensor.

When the IAT Sensor Signal circuit is grounded, IAT should read 147°C (247°F) or greater. This helps to determine if problem is in the IAT Sensor Signal circuit or the IAT sensor ground circuit.


P1111 **************************

Circuit Description
The Intake Air Temperature (IAT) sensor is a thermistor, or variable resistor, that varies resistance based on temperature. Low temperature will result in a high signal voltage. If the IAT reading is -35°C (-31°F)or lower with the ECT sufficiently hotter than the IAT, the PCM sets DTC P1111.

Conditions for Setting the DTC
Test Conditions
DTCs P0101, P0102, P0112, P0113, P0117, P0118, and P0502 not set.
Engine speed 500 RPM or greater for 10 seconds.
MAF input 60 grams per second or less.
Vehicle speed 50 MPH or less.
5 seconds have passed with vehicle speed greater than 7 MPH since the engine was started.
Engine coolant temperature 0°C (32°F) or greater, or engine coolant temperature less than 0°C (32°F) and IAT at least 27°C (81°F) less than engine coolant temperature.
Failure Condition
IAT -35°C (-31°F) or less with the above test conditions met.

Action Taken When the DTC Sets

The Malfunction Indicator Lamp (MIL) will not illuminate.
No message will be displayed.
Conditions for Clearing the DTC

A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
Use a scan tool to clear DTCs.
Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.
Diagnostic Aids
If a faulty sensor is suspected refer to Temperature vs Resistance table.

If fault is not present perform Powertrain Ground Check and also review Failure Rec. to determine conditions under which and how long ago the DTC set.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.

If DTC P0111 is also set, diagnose it first because it may help to pinpoint a faulty IAT sensor.

Checking for intermittent circuit faults that may cause a high IAT reading.



As for checking codes...the 96-97 cluster is different then the 92-95-

On the 96/97, push the OFF button and the top (warmer) end of the PASS rocker switch.


It sounds as if the IAT sensor is either unplugged or has completely failed.

Logan
 

·
Registered
Joined
·
78 Posts
Hey Dave,how can anyone post another reply after a full boat technical diagnostic answer like that? See- ask a simple question and get more than you bargained for. How was your Christmas Holiday!!! Ours was great here. As usual after an answer from Dave Logan you should have no more questions about your cars electronics. Logans the best of the best in diagnostic repair.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #4
Wow, Yes this was really way beyond what I would have hoped for. Thanks for a great description.

However, it does leave a few questions from this novice owner:

1) Where do I locate the IAT, and in general where do I find enough information to work my way round the N* in more details, and

2) How do I get to the point where I can see the IAT readout on the display ? I do have the 96/97 dashboard.

Thank you again for the detailed answer,

Leif
 

·
Registered
Joined
·
1,121 Posts
We have the GM software....so all the info was simply 'copy and paste.' Very fast to do.

The IAT sensor is typically mounted on or very near the air cleaner assembly. As for seeing the data on the IPC. It can be done....but we never use the onboard diagnostics. Its easier and faster to use our Tech2.

Logan
 

·
Registered
Joined
·
49 Posts
We have the GM software....so all the info was simply 'copy and paste.' Very fast to do.

The IAT sensor is typically mounted on or very near the air cleaner assembly. As for seeing the data on the IPC. It can be done....but we never use the onboard diagnostics. Its easier and faster to use our Tech2.

Logan

Does anyone have a diagram or picture to help me identify the IAT and location?
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,281 Posts
For a '97 your best bet is a Helm Factory Service Manual - eBay or www.helminc.com. I think your IAT sensor is plugged into the side of the air intake piping near the airbox. In 2002 it was incorporated into the MAF body.

Take a look at the pictures alongside the part description in www.rockauto.com. Drill down to your car, Fuel/Air or Emissions, and click on the picture for a larger view or click on the "!" icon.

Heck of a way to resurrect a 5 year old thread !! You must be one of the few who studies........
 

·
Registered
Joined
·
49 Posts
YUP. Right in side the cleaner. It was unplugged.....

This service engine light has been on since the last timeI had the oil changed. HMMMMMMM....

Honest mistake or an attempt to ensure repeat biz....????
 
1 - 10 of 10 Posts
About this Discussion
9 Replies
6 Participants
Ranger
Top