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General Smog Check

1997 Mercury Grand Marquis Drive Cycle

I just had the O2 sensors replaced on my 1997 Mercury Grand Marquis. I had trouble codes P0171 and P0174. The check engine light has since turned off but the emission monitors are not ready. I'm wondering how many miles I need to drive the car before I can get it smog checked? I'd prefer to get it to pass the first time. Thanks!


We understand your Mercury Grand Marquis is having difficulty getting certain emission monitors to complete (become Ready). First off we should mention, at the time of this posting, the EVAP monitor is the one monitor allowed to be incomplete and your vehicle still pass the smog check. So... if after you perform the drive cycle a few times and are able to get the other monitors ready, and the EVAP monitor remains the only monitor which is not, no need to worry, your Grand Marquis can pass the smog check. Visit a local smog station and obtain the inspection.

Follow the Mercury Grand Marquis drive cycle below. The required monitors should become ready to pass the smog inspection simply by driving your vehicle for 200-300 miles and over the course of a few days. Due to individual driving habits/patterns, sometimes the drive cycle parameters are not met with ordinary driving, and following the Mercury Grand Marquis drive cycle is necessary.

Take extra caution when performing drive cycles on public roadways, obeying all traffic laws. Perform the drive cycle below at your own risk. You may also seek repair assistance from a Mercury dealership. They will be able to complete the drive cycle using manufacturer specific scan tools. If after performing the drive cycle twice your Grand Marquis is still unable to pass the smog check because its monitors (or monitor) are incomplete, please seek assistance from a smog check repair center or Mercury dealership.

How To Complete Mercury Grand Marquis Drive Cycle

The following procedure is directly from Mercury and designed to complete the OBDII monitors required to get your Mercury Grand Marquis to pass the OBDII Monitors portion of the smog check, also known of the I/M readiness test. You may use a scan tool in order to monitor the status of the emission monitors as your vehicle is being driven.

START HERE - Drive Cycle Recommendations:

1.Emission monitors (readiness flags) will complete quicker when using a "steady foot" driving style during cruise or acceleration modes. Operating the gas pedal in a "smooth" manner will minimize the time required for monitor completion.

2. Fuel tank level should be between 1/2 and 3/4 fill during the drive cycle in order to allow the EVAP monitor to run. 

3.The Evaporative Monitor can only operate during the first 30 minutes of engine operation. During the EVAP portion of the drive cycle, drive in a smooth fashion to minimize "fuel slosh". 

Drive Cycle Preparation - 1. If using a scan tool, go ahead and connect it now. Turn key on with the engine off. Cycle key off, then on. Select the appropriate vehicle make and model on your scan tool. Start your Mercury Grand Marquis WITHOUT returning to Key Off. Idle the vehicle for 15 seconds, and then drive at 40 MPH until engine coolant temperature is at least 170°F, which is normal engine operating temperature. 10 to 15 minutes of drive will achieve this.

HEGO Monitor - 5. Cruise at 40 MPH for up to 4 minutes.

EVAP Monitor - 6. Cruise at 45 to 65 MPH for 10 minutes (avoid sharp turns and hills).

Catalyst Monitor - 7. Next, drive your Mercury Grand Marquis in stop and go traffic conditions. Include five different constant cruise speeds, ranging from 25 to 45 MPH over a 10 minute period.

EGR Monitor - 8. From a stop, accelerate to 45 MPH at 1/2 to 3/4 throttle. Repeat this pattern 3 times.

SEC AIR/CCM (Engine) - 9. Bring your Mercury Grand Marquis to a stop. Idle with transmission in drive (neutral for M/T) for 2 minutes.

CCM (Trans) - 10. Start from a stop and in overdrive, then moderately accelerate to 50 MPH and cruise for at least 15 seconds. Stop the vehicle and repeat without overdrive to 40 MPH cruising for at least 30 seconds. While at 40 MPH, activate overdrive and accelerate to 50 MPH and cruise for at least 15 seconds. Stop for at least 20 seconds and repeat step 10 five times.

Misfire & Fuel Monitors - 11. From a stop, accelerate to 65 MPH. Decelerate at closed throttle until 40 MPH (no brakes). Repeat this 3 times.

Readiness Check - 12. If using a scan tool, go ahead and access the ON-Board System Readiness (OBDII monitor status) function on the scan tool. Determine whether all emission monitors have completed.

EVAP Monitor "Bypass" - 13. Park vehicle for a minimum of 8 hours. Repeat steps 2 through 12.

posted by SmogTips Support

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