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Cat IM reset...

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Old January 20th, 2016, 9:14 PM
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Default Cat IM reset...

I have two monitors I need to reset before Cali SMOG on my 96 4 cyl. I read the Drive Cycle procedure, but can't seem to get the last two done. I've heard the Evap one can take 40 cycles and would get a pass during the check, but I'm concerned that a Cat monitor would get closer scrutiny. Can anyone give me a drive that would reset the Cat monitor?
Old January 20th, 2016, 11:25 PM
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I may have found the answer, although it's not an expedient one...

HOLD STEADY: Hold steady speed once again. This time at 88km/hr (55mph) for five minutes. During this time, in addition to running the self-tests as during the first HOLD STEADY step, the ECU will perform the catalyst monitor diagnostics. If the catalyst (Catalytic Converter) is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst,or in order to Complete the CAT Monitor.

Note, this says it may take 5 complete driving cycles to set. Once again, I am awestruck by the complete stupidity of how these computers have to be reset before meeting certification.

This was taken from a DuraMax post, but the basics were so similar that I thought it would help others with older engines. The entire post follows:

How to Perform Chevy Duramax Drive Cycle
The following is a Chevrolet OBDII Drive Cycle Pattern. (Obey all traffic laws while performing drive cycles. Perform acceleration steps only on highways. If you feel you will be unable to perform the drive cycle safely, seek assistance from a Chevy dealership or smog check test & repair center).
COLD START: Begin from Cold Start, and ignition key in OFF position for at least 1 hour. Ensure fuel tank is between 1/4 and 3/4 full. Engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
IDLE TIME: Run engine (do not drive) for 2 1/2 minutes with the air conditioner on and rear defroster on. During this period the ECU will be running the Oxygen Sensor Heater self-test, Air Injection System Passive Air test, EVAP Purge "No Flow" test, Misfire Detection.
ACCELERATE: Turn off the air conditioner and rear defroster and begin driving. As soon as possible apply half throttle until 88km/hr (55mph) is reached. The ECU will now run self-tests on the Misfire Detection, Fuel Trim, and EVAP Purge Flow.
HOLD STEADY: Now hold your speed steady at 88km/hr (55mph) for three minutes. During this time the Oxygen Sensor O2 response, Air Intrusive (AIS System), EGR Flow, Purge Valve, Misfire Detection, and Fuel Trim diagnostics will be performed.
DECELERATE: During this step you want to slowly let off the accelerator pedal. Do not brake or shift in order to slow down (don't press the clutch if equipped). It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). The ECU will once again self-test the EGR System, EVAP Purge System and Long Term Fuel Trims.
ACCELERATE: Go ahead and accelerate again at 3/4 throttle until 88-96 km/hr (55-60mph) is reached. This will perform the same self tests as during the first acceleration step.
HOLD STEADY: Hold steady speed once again. This time at 88km/hr (55mph) for five minutes. During this time, in addition to running the self-tests as during the first HOLD STEADY step, the ECU will perform the catalyst monitor diagnostics. If the catalyst (Catalytic Converter) is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst,or in order to Complete the CAT Monitor.
DECELERATE: This will perform the same diagnostics as in the first Deceleration. Remember not to press the brakes or shift gears (don't press the clutch if equipped).
This completes the Chevy Duramax drive cycle, and should make Complete/Ready all required Emission Monitors requried to pass the smog test. If you have access to an OBDII scan tool you can check the emission monitors for READY status before revisiting the smog check center.


posted by SmogTips Support 01-14-2016 04:23 PM




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