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How To Perform GMC Sonoma Drive Cycle and Make Emission Monitors Ready

I went to a smog shop and was told that the air pump monitor was not ready on my GMC Sonoma. I drove for 100 miles and took it back and they told me the same thing again. Is there any way I can fix this?

Answer:  

We should begin by noting that the secondary air injection monitor which checks for the performance of the air injection system and air injection pump requires the monitor to start from a cold (engine) start. Once the engine warms up, the monitor is done checking the air injection pump and will continue on checking the performance of the entire AIR injection system. With that said, it's not the number of miles driven which resets the air injection monitor, rather the number of cold starts required to get all the other parameters required for the air injection monitor to to run, being met. A cold start is considered starting the engine after the vehicle has sat for at least 8 hours. Since the air injection monitor takes into effect ambient air temperate, it is best to perform a cold start in the mornings.

In most cases, all the monitors should run during normal vehicle operation. However, due to different driving habits, the criteria required to run a monitor may not always be met. Following the GMC Sonoma drive cycle below should allow all emission monitors to complete. The drive cycle must be followed accurately. Take extra caution when performing the drive cycle on public roadways. Perform the drive cycle at your own risk. If you feel you might not be able to perform the drive cycle safely, or obey all traffic laws, seek the assistance of a smog check repair station which will be able to perform the drive cycle on a dynamometer and be utilizing specialized OBD II drive cycle readiness tools/scanner/computer.

How to Perform a GMC Sonoma Drive Cycle

The GMC Sonoma drive cycle below will complete or make ready your truck's emission monitors, including the EVAP monitor, Oxygen Sensor monitor, EGR monitor, and Secondary Air Injection. If after completing the drive cycle your truck will still not complete the Secondary Air Injection monitor we have to recommend visiting the dealership or the smog check referee's office.

We have not been able to find any TSB concerning the air injection monitor not being able to set on a GMC Sonoma but if the smog check referee office is unable to find/diagnose the fault which is causing the air injection monitor to not set they may issue you a one time smog check waiver; allowing you time to research this fault further.

START HERE

A. Cold Start: Begin from Cold Start, and ignition in OFF position for at least 1 hour. Ensure your GMC Sonoma's fuel tank is between 1/4 and 3/4 full. Engine coolant temperature must be below 122°F and within 11°F of the ambient air temperature. Do not leave the key on prior to the cold start or the heated oxygen sensor (O2) diagnostic may not run. 

B. 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. 

C. Accelerate: Turn off the air conditioner and rear defroster and begin driving your Sonoma. As soon as possible apply half throttle until 55mph is reached. The ECU will now run self-tests on the Misfire Detection, Fuel Trim, and EVAP Purge Flow. 

D. Hold Steady Speed: Hold your speed steady at 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. 

E. Decelerate: During this step slowly let off the accelerator pedal. Do not brake or shift in order to slow down. It is important to let your Sonoma coast along gradually slowing down to 20 mph. The ECU will once again self-test the EGR System, EVAP Purge System and Long Term Fuel Trims. 

F. Accelerate: Accelerate again at 3/4 throttle until 55-60mph is reached. This will perform the same self tests as during the first acceleration step. 

G. Hold Steady Speed: Hold steady speed once again. This time at 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. 

H. 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 ends the drive cycle. Performing the drive cycle on your GMC Sonoma at least twice will ensure all monitors run, including the EVAP monitor, and your GMC Sonoma is ready for the smog check.

Should you want to perform specific Monitor self-tests follow the steps below.

Catalyst Monitor (CAT): 

Prerequisite: No trouble codes present, Intake Air Temperature (IAT) above 32 Degrees (F), Engine Coolant Temperature (ECT) is above 167 Degrees (F); Mass Air Flow sensor is indicating greater than 15 gm/s, engine load is below 63% and steady, engine speed is below 3000 RPM. 

1. Idle vehicle 5 minutes (achieve closed loop) 

2. Drive 5 min at steady speed above 55 mph 

3. Drive 2 min at steady 40 mph 

4. Drive 2 min at steady 55 mph 

EGR Monitor (EGR): 

Prerequisite: No trouble codes present, Engine Coolant Temperature (ECT) is above 75 Degrees (F); barometric pressure (BARO) above 72kPa.

1. Idle vehicle 5 minutes (achieve closed loop) 

2. Accelerate and drive for 1 min at steady speed above 50 mph 

3. Slow vehicle down to 20 mph. Do not use brake clutch, or shift gears. 

4. Repeat steps two and three 5 times. 

GMC runs their EGR monitor during the deceleration portion of the drive cycle.  

Evaporative Monitor (EVAP): 

Prerequisite: No trouble codes present, Fuel tank between 1/4 and 3/4 full.

1. Drive 5 min at steady speed between 30 and 60 mph 

2. Stop vehicle and idle engine for 4 minutes.

3. Turn engine off. Remove ignition key.

The ECU will run the EVAP Monitor once the engine has been shut down and ignition turned off.

O2 Sensor Monitor (O2): 

Prerequisite: No trouble codes present, Intake Air Temperature (IAT) above 32 Degrees (F); Engine Control Temperature (ECT) is above 167 Degrees (F)

1. Idle vehicle 4 minutes (achieve closed loop) 

2. Drive 3 min at steady speed above 50 mph 

3. Drive 2 min at steady 40 mph 

4. Drive 2 min at steady 50 mph


posted by SmogTips Support 04-04-2018 12:37 PM
 


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