2003 Cadillac Escalade Ext



May, 15, 2009 AT 10:57 AM

2003 Cadillac Escalade Ext V8 All Wheel Drive Automatic 110000 miles

I recently purchased a 2003 Cad Escalade Ext with 110,000 miles that runs and looks terrific. The vehicle has been maintained well.
The previous owner has upgraded the exhaust system with performance muffler with dual pipes. My check engine light came on recently and I had the code checked to reveal that both catalytic converters were malfunctioning. The mechanic said that this was unlikely so he cleared the code. I drove it for about 350 miles over a 3-day period then the check engine light came back on. I took it in for a emission test to determined if the cats were doing what they are suppose to do and I passed the test with flying colors HC limit 150 reading 10 CO limit.07 reading.05. This test was done with the check engine light on. My question: what is causing the check engine and why did the problem not show up in the test? Any help would be appreciated. Thanks.


11 Answers



May, 29, 2009 AT 10:44 PM

It is called catalyst monitoring. The post O2 sensors are basically in place to check catalyst efficiency. What happens is when the front sensors are working, the rear(post) sensors should be stable. If the rear sensors are mimicking the front, it tells the ecm that the cats are not working at oxidizing hc and co. And triggers efficiency faults. You would not notice any running faults, and gas readings are correct out the tailpipe because the pre-cat sensors are doing there job. Only fixed with catalyst replacement as far as I know. Do you have a service contract?



June, 4, 2009 AT 8:58 PM

Thank you for responding! If I replaced the cats would I not still incur the same problem with after the cat sensors? Again, I passed emissions with flying color. Therefore can I not assume the cats are doing what there are supposed to do? I read many places where owners are installing O2 simulators. Is this an option in your opinion?



June, 5, 2009 AT 12:21 AM

The engine could run efficiently enough these days, that a cat may not even be necessary, but it's that federal thing. I am not a real big fan of anything simulator, seems to always end up a waste of money. It is not the post-cat sensors at fault here, it is the fact that they are deeming the cats non-functional, based on the ecm's programmed criteria. In a nutshell, the pre-cat sensors are fluctuating voltage based on exhaust O2 content, this voltage typically ranges.1 to 1.0 in an oscillating wave form. If the post cat sensors are fluctuating along a similar path, theoretically the cats are doing nothing. If the post-cat sensors were lingering somewhere around the half way(.40/.50v) Then the cats are lit off and oxidizing. What is happening to trigger your codes, are the post sensors are mirroring the pre. My guess on the reason that both have failed, is that one has been failed for some time, and the other joined. If this vehicle had less than 80k(maybe even 100k) miles, these would be covered under manufacturers emissions warranty. I have not seen a vehicle with both banks failed since catalyst monitoring emerged.



June, 5, 2009 AT 10:40 AM

Gstacey: Thank you for your insight. I completely understand the situation now. Unfortunately my vehicle is over 100K and therefore not covered under warranty. I will source a couple catalytic converters. Wish me luck because the dealer wants 1000 dollars (installed) per side. Is it worth exploring a universal cat?



June, 5, 2009 AT 9:44 PM

That is possibly why the previous owner chose not to replae them. Aftermarket ones should function, you may not get the service life out of them, as opposed to O.E.



June, 8, 2009 AT 10:03 PM

Thanks for your help.



September, 24, 2009 AT 12:46 PM

I'm having a similar situation with my '01 Chevy Blazer. 4.3L V6, Auto, 186,000 mi and I'm the original owner. The Catalyst Monitoring Status won't come out of " Incomplete" but I'm not getting any engine codes. There's also a Evaporative System monitoring showing incomplete status too. They're keeping my truck from passing the state inspection and I'd like to get it taken care of. Did you change the cats and did that correct the problem? Thank you for your time.



September, 24, 2009 AT 10:20 PM

In your situation jerrylmo, you probably do not need cat(s). Has the battery been disconnected, or a fault repaired with codes cleared being issued. This will reset all I/M monitors to unready(in your case incomplete). It could take some time to change, because it needs specific criteria met to run the tests. I forwarded a typical drive cycle list for your vehicle, and it's tests that run.

System Status and Drive Cycle For Inspection/Maintenance
The System Status selection is included in the scan tool System Info menu.

Several states require that the I/M (OBD ll system) pass on-board tests for the major diagnostics prior to having a vehicle emission inspection. This is also a requirement to renew license plates in some areas.

Using a scan tool, the technician can observe the System Status, complete or not complete, in order to verify that the vehicle meets the criteria to comply with local area requirements. Using the System Status display, any of the following systems or combination of systems may be monitored for I/M Readiness: " The catalyst

" The evaporative emission (EVAP) system

" The heated oxygen sensors (HO2S)

" The heated oxygen sensor (HO2S) heater

" The exhaust gas recirculation (EGR) system

" The secondary air injection (AIR) system

Important: The System Status display indicates only whether or not the test has been completed. The System Status display does not necessarily mean that the test has passed. If a Failed Last Test indication is present for a DTC associated with one of the above systems, diagnosis and repair is necessary in order to meet the I/M requirement. Verify that the vehicle passes all of the diagnostic tests associated with the displayed System Status prior to returning the vehicle to the customer. Refer to the Typical Drive Cycle table, more than one drive cycle may be needed, to use as a guide to complete the I/M System Status tests.

Following a DTC info clear, System Status clears for one or all of these systems. Following a battery disconnect or a PCM replacement, all System Status information clears.

Typical Drive Cycle Diagnostic Time Schedule for I/M Readiness

Vehicle Drive Status
What is Monitored?

Cold Start, coolant temperature less than 50 C (122 F)

Idle 2.5 minutes in Drive (Auto) Neutral (Man), A/C and rear defogger ON
HO2S Heater, Misfire, Secondary Air, Fuel Trim, EVAP Purge

A/C off, accelerate to 90 km/h (55 mph), 1/2 throttle.
Misfire, Fuel Trim, Purge

3 minutes of Steady State - Cruise at 90 km/h (55 mph)
Misfire, EGR, Secondary Air, Fuel Trim, HO2S, EVAP Purge

Clutch engaged (Man), no braking, decelerate to 32 km/h (20 mph)
EGR, Fuel Trim, EVAP Purge

Accelerate to 90-97 km/h (55-60 mph), 3/4 throttle
Misfire, Fuel Trim, EVAP Purge

5 minutes of Steady State Cruise at 90-97 km/h (55-60 mph)
Catalyst Monitor, Misfire, EGR, Fuel Trim, HO2S, EVAP Purge

Decelerate, no braking. End of Drive Cycle

Total time of OBD II Drive Cycle 12 minutes



September, 25, 2009 AT 9:09 AM

I have a couple of electronic tools that are helping me to see what's going on. One is the AutoTap ECM software that runs on a Palm T2 and I also have a Snap On MT2500 scanner with cartridges for '06 domestic cars.
The AutoTap will read the system monitoring status on the parameters listed in your reply. I noticed, like you said, after clearing the codes, all the monitoring status items went to " incomplete". After a few miles of driving all of them went back to complete except for Cat Monitoring Status and Evap Monitoring.
Any suggestions on which sensors I could watch to get some clues? Thanks, Jerry



September, 25, 2009 AT 10:43 PM

The problem is, those two parameters can sometimes take a while. If either of your scan tools shows 'not run since codes cleared', look at which tests have not run. Stuff like P0442 and P0446 are evap leak tests, see if they have run. If they haven't, that is one circumstance as to why evap is not showing ready. Is it setting any codes that may prohibit tests from running? Here is the chart for P0446 for example, to show the criteria under which this test runs. You will also see service bay test in the chart, if your scan tool has this feature, that forces the evap test to run.

DTC P0442
Circuit Description
The powertrain control module (PCM) tests the evaporative emission (EVAP) system for the following conditions: " Large and small leaks

" Excess vacuum

" Purge flow during non-commanded conditions

" Fuel level and fuel pressure sensor faults

" EVAP purge and vent valve faults

The PCM monitors the fuel tank pressure sensor in order to determine the level of vacuum or pressure in the EVAP system. The PCM commands both the EVAP purge solenoid and the EVAP vent valve ON when the Conditions for Running the DTC are met in order to apply an engine vacuum to the EVAP system. The PCM commands the EVAP purge solenoid OFF once the system has reached a predetermined level of vacuum. The EVAP system should HOLD the vacuum in the sealed system. The PCM sets this diagnostic trouble code (DTC) in order to indicate a small leak if the EVAP system fails to hold a predetermined level of vacuum for a predetermined length of time. This DTC sets after failing the above test twice.

Conditions for Running the DTC
" DTCs P0107, P0108, P0110, P0112, P0113, P0115, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0443, P0449, P0452, P0453, P1106, P1107, P1111, P1112, P1114, P1115, P1121, or P1122 are not set.

" The barometric pressure (BARO) is more than 75 kPa.

" The fuel level is between 15-85 percent of full capacity.

" The throttle position (TP) sensor angle is less than 75 percent.

" The vehicle speed is less than 102 km/h (65 mph).

" The engine coolant temperature (ECT) is between 4-30 C (39-86 F).

" The intake air temperature (IAT) is between 4-30 C (39-86 F).

" The start up ECT and IAT are within 9 C (16 F) of each other.

Conditions for Setting the DTC
The vacuum in the EVAP system decays or leaks at too fast a rate.

Important: This DTC does NOT report a first failed test. A first fail of this DTC will have a scan tool status as Not Run. Use the scan tool data display parameter of EVAP test result to determine if this DTC has failed or passed for this ignition cycle.

Action Taken When the DTC Sets
" The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

" The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC
" The control module turns OFF the malfunction indicator lamp (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.

" Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
Important: " Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

" An accurate indication of fuel level is required for the PCM to properly pass or fail this DTC. Always diagnose fuel level sensor DTCs before performing this DTCs diagnostic table. Always inspect for fuel level sensor DTCs stored as History.

" The Service Bay Test may have to be performed in cold ambient air temperatures when the vehicle is running a winter grade fuel. The scan tool displays a message when the service bay test does not run.

" Inspect for charcoal release from the vapor canister. Refer to Evaporative Emission System Cleaning procedure.

Conditions for Running the Service Bay Test
" The battery voltage is between 10.5-17.5 volts.

" The fuel level is between 15-85 percent of the full capacity.

" The engine temperature is between 3.5-35 C (38-95 F).

Perform a physical inspection of the EVAP system. Inspect for the following conditions: " A loose, missing, defective, or incorrect fuel tank cap

" Incorrectly routed or defective EVAP system vacuum and vapor lines

" A malfunctioning or damaged vapor canister

" Charcoal release from the vapor canister--Refer to Evaporative Emission System Cleaning.

The vacuum and pressure in the EVAP system is measured in inches of water (H2O). Most gauges measure vacuum in inches of mercury (Hg) and pressure in pounds per square inch (psi). The following shows how the values compare: in H2O
in Hg

1in H2O
0.07 in Hg
0.0361 psi

5 in H2O
0.36 in Hg
0.180 psi

10 in H2O
0.73 in Hg
0.361 psi

15 in H2O
1.10 in Hg
0.541 psi

Test Description
The numbers below refer to the step numbers on the diagnostic table.

This step verifies that a failure condition is active.

This step verifies that repairs are complete and that no other condition is present.


Schematic Reference: Emission Hose Routing Diagram and Engine Controls Schematics

Did you perform the Diagnostic System Check-Engine Controls?
Go to Step 2
Go to Diagnostic System Check - Engine Controls

Does the scan tool indicate DTC P0443 or DTC P0449 are also set?
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3

Inspect the EVAP system for the following conditions: " Loose, missing, or damaged service port dust cap and/or schrader valve.

" Loose, incorrect, missing, or damaged fuel fill cap.

" A damaged EVAP canister purge valve.

Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
Inspect the EVAP system for the following conditions: " Disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses.

" A damaged EVAP canister vent valve or EVAP canister

Did you find and correct the condition?
Go to Step 6
Go to Step 4

With a scan tool, capture and record the fail record data and clear the DTCs.
Perform the Service Bay Test. Refer to Service Bay Test.
Does the scan tool indicate that the service bay test passed?
Go to Diagnostic Aids
Go to Step 5

Important: Always zero the EVAP Pressure and vacuum (in. H2O) gauges on the EVAP Pressure Diagnostic Station before proceeding with diagnosis.

Install the J 41415-40 Fuel Fill Cap Adaptor.
Connect the J 41413 Pressure/Purge Diagnostic Station to the fuel fill cap adaptor.
Turn ON the ignition, with the engine OFF.
With the scan tool, seal the EVAP system.
With the pressure/purge diagnostic station, continuously pressurize the EVAP system to the specified value.
Important: It may be necessary to partially lower the fuel tank to inspect components located in the upper portion of the tank.

With the J 41416 Ultrasonic Leak Detector inspect for leaks in the following locations: " The EVAP system purge pipe--Refer to Evaporative Emission Hoses/Pipes Replacement - Engine, Evaporative Emission Hoses/Pipes Replacement - Chassis/Canister or Evaporative Emission Hoses/Pipes Replacement - Engine/Chassis.

" The EVAP vapor pipe--Refer to Evaporative Emission Hoses/Pipes Replacement - Canister/Fuel Tank.

" The EVAP vent hose

" The fuel fill pipe/hose and fuel fill cap--Refer to Filler Tube Replacement.

" The EVAP canister--Refer to Evaporative Emission Canister Replacement.

" The EVAP canister vent valve--Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement.

" The EVAP canister purge valve--Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement.

" The fuel sender assembly and/or seal--Refer to Fuel Sender Assembly Replacement.

" The fuel tank pressure (FTP) sensor seal--Refer to Fuel Tank Pressure Sensor Replacement.

" The fill limiter vent valve, pressure relief valve, rollover valves, permanent EVAP pipes and/or fuel tank--Refer to Fuel Tank Replacement.

Did you find and correct the condition?
15 in H2O
Go to Step 6
Go to Diagnostic Aids

Perform the Service Bay Test. Refer to Service Bay Test.

Does the scan tool indicate that the service bay test passed?
Go to Step 7
Go to Step 2

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?
Go to Diagnostic Trouble Code (DTC) List
System OK

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