jeep58

My nephews jeep which I am considering purchasing has a new battery and alternator, The OB2 scanner shows no codes buy the yellow triangle lights up on scanner saying emissions, how do you get this light to go out for inspection?

Noah911

The yellow triangle possible emmissions problem light is supposed to turn itself off on its own, ussually simply by driving around normally. I found sometimes it requires for you to actually carry out the different 'drive cycles'.. in order for the ECU-PCM to finish certain specific readiness tests. That is what is happening is the PCM has not been able to complete all of the emmissions readiness testing procedures like it is supposed to...

The drive cycles are specific procedures, and it sounds like you will have to actually follow them exactly how they are detailed.

This should be right, and I believe these are them:

Did you clear any trouble codes recently? If so, your Jeeps emission monitors were cleared as well.. In other words, the emission monitors (also known as readiness flags) were erased, and now need to be completed again. In order to make the monitors ready, or complete, you will need to drive your Jeep in a specific drive pattern, known as a Drive Cycle. Typically, driving 200-300 miles over the course of a week, in both city and highway traffic is enough to complete the monitors. Sometimes however, the driving pattern required is not met by regular driving, and the specific segments of the entire Drive Cycle must be performed individually.

Be very careful performing the drive cycle on public roadways. There are many starts and stops, as well as varying driving speeds. Smog check repair stations suggest performing drive cycles using dynomometers. If you feel you may be unable to perform the drive cycle safely seek assistance from a Jeep dealership service center, or a smog check repair station.

During all sections of the drive trace make sure your gas tank is between 1/4 to 3/4 full of gas; never below or above the 1/4-3/4 marks.



(copy and paste):

Catalyst Monitor Drive Trace

Pre-Conditioning Requirements:

- MIL must be off.

- No DTCs present.

- Fuel level is between 15% and 85% full.

- ECT above 70º F.

- Engine must have run at least 90 seconds

- Engine between 1,350 & 1,900 rpm.

Driving Procedure

1) Idle vehicle for five minutes (to reach normal engine operating temperature and closed loop operation).

2) Drive with a steady vehicle speed between 30 & 45 mph for 2 minutes.

EGR System Monitor Drive Trace - Vacuum controlled

Pre-Conditioning Requirements:

- MIL must be off.

Driving Procedure

1) Idle vehicle for five minutes (to reach normal engine operating temperature and closed loop operation).

2) Drive with a steady vehicle speed between 40 & 60 mph for 8 minutes.

EGR System Monitor Drive Trace - Electronic

Pre-Conditioning Requirements:

- MIL must be off.

- MAP must be between 0-60 KPa.

- Engine speed between 500-850 rpm.

- ECT is above 180º F (90º C).

- No misfire pending or matured fault should be present.

- A/C clutch, PS Switch and Cooling fans do not change state (turn off).

Driving Procedure

1) Idle vehicle for five (5) minutes (to reach normal engine temps and get in to closed loop operation).

2) Drive with a steady vehicle speed between 40 & 60 mph for 2 minutes.

3) Idle vehicle for three (3) minutes.

Evaporative System Monitor Drive Trace

Trace 1: Standard Type

Pre-Conditioning Requirements:

- MIL must be off.

- No Evaporative DTCs present.

- Fuel level is between ½ and full.

(Note: monitor may still run with tank fill between 15% and 85%).

Driving Procedure

1) Idle vehicle for five minutes (to reach closed loop operation).

2) Drive with a steady vehicle speed between 30 and 45 mph for 2 minutes.

Trace 2: Leak Detection Pump

Pre-Conditioning Requirements:

- MIL must be off.

- No Evaporative DTCs present.

- Fuel level is between 30 & 85 % full.

Driving Procedure

1) Cold soak vehicle, start and idle vehicle for 4 minutes.

2) Drive in-town (stop and go) for 5 minutes, using smooth acceleration and deceleration.

3) Stop and idle vehicle for 4 minutes.

O2 Sensor Monitor Drive Trace

Pre-Conditioning Requirements:

- MIL must be off.

Driving Procedure

1) Idle vehicle for five minutes (to reach closed loop operation).

2) Drive with a steady vehicle speed above 25 mph for 2 minutes.

3) Stop and idle for 30 seconds.

4) Smoothly accelerate to a speed between 30 and 40 mph.

5) Repeat steps 3 & 4 five (5) times.

O2 Sensor Heater Monitor Drive Trace

Pre-Conditioning Requirements:

- MIL must be off.

Driving Procedure

1) Idle vehicle for five minutes (to reach closed loop operation).

2) Shut engine off and leave vehicle off for ten minutes.

(end copy and paste)

Hopefully this helps? I believe these to be the specific Drive Cycle patterns it sounds like you will need to perform in order for your ECU-PCM to complete its readiness testing protocol.

(edited to add):
Having just replaced the battery in your nephews Jeep is probably the reason...

jeep58

Battery and alternator has been replaced and the jeep has not been driven prior to that he drove jeep with bad alternator and killed battery. There are no other codes pending or check engine light on! So what you are saying is to drive the jeep for a while and this should clear the emission light right? Thanks for the reply again !!

Noah911

You are very welcome. Yes sir, it needs to be driven. Driving it probably 1-2 hundred miles in varying operational conditions should normally do it. Make note of the level of gasoline in the gas tank. That should not really be an issue though, because I think we usually mostly all have something between 15-85% full tank while we are out regularly driving.

(edited to add):
I was meaning to also tell you about the standards set for emmissions testing. You are allowed to have a yellow triangle possible emmissions problem light.. They give leeway here with this one. So long as the PCM has completed the majority of its readiness tests, they have to pass your vehicle. Depending on your state and specific location, they will allow having one, or two.. of the readiness tests to have not been completed.

jeep58

Thank you The jeep is has the 4.0 motor which I like it had a lot of work done on it by a mechanic that has known the the jeep for two previous owners one being my sister. I am going to buy the jeep and hope it will hold up for awhile I have owned a 4.0 jeep grand cherokee since 2001 this will be my 3rd one !

Noah911

I agree with that. The XJ, ZJ, and WJ's are my favorite vehicles, and the 4.0L is my favorite engine!

Aside from a Camaro

jeep58

Yes many years ago I had a 69 mustang mach 1 , sold it and regretted it ever since !

Noah911

My favorite vehicle is an all black 2015 Z28 race-tuned at the Virginia International Raceway. Its totaly out of this world!