Removing the MAF Sensor...no check engine light?

duncanm · **Joined:** Fri Dec 06, 2013 9:17 am **Posts:** 4

Hi all,

I just purchased a 2005 Jeep Liberty Limited CRD with 49,000 miles. I was expecting good gas mileage but my wife was averaging 19 mpg with a mix of city and highway. So i was doing some research and found the noob guide. I changed the fuel and air filter, cleaned the MAP sensor (which was really dirty), and also unplugged the MAF sensor. After I did all this I drove the jeep back and fourth to my wifes work and averaged 23mpg, but the weird thing is that the CEL never came on. Has anyone had this issue?

Also, my engine is running too cool, just a hair over the first quarter. I have a new thermostat on the way.

Thanks for your help!

kjjet · **Posted:** Fri Dec 06, 2013 9:47 am

The only way this could be is, your CRD has a MOD GDE or SERG. OR lamp is not operating?

With the engine off turn the key forward to RUN, the CEL (little engine) should be on. If it is? you have a tune. Which is very good.

FYI...the OEM thermostat is junk. Even a new one may fail in a short time. The inline ones work longer for under $20.

Good luck
KJJET

duncanm · **Joined:** Fri Dec 06, 2013 9:17 am **Posts:** 4

I will have to check to see if the lamp is operating when I get home. I find it hard to believe it has a tune because I purchased it from the original owner, an old couple, and they said they never did a tune or anything aftermarket. Also, right before I bought it they took it to the dealer and had all the recalls updated, I assume this included the F37. Is there an easy way to see if it has an aftermarket tune? Also, I did order an inline thermostat instead of the factory. Thanks.

kjjet · **Posted:** Fri Dec 06, 2013 10:20 am

As far as telling if you have a tune? If it has I SERG tune there will be a little box. (not sure were they place them) GDE tune is just a flash of the ECU (Engine Control Unit) so there is no way to see any difference. Pulling the MAF sensor is the best way. Light on = no mod. No light = has mod.

Good luck
KJJET

dgeist · **Posted:** Fri Dec 06, 2013 10:23 am

kjjet wrote:

The only way this could be is, your CRD has a MOD GDE or SERG. OR lamp is not operating?

KJJET

SEGR doesn't remove the need for a functional MAF sensor, it still takes in the values and passes them onto the ECM, just that it fakes the resistance on the feedback pin for the EGR accordingly with an analog step function based on input current. GDE tune is more likely, methinks. I'm guessing GDE could confirm if you pull the serial number on the case of the ECU and call them.

Dan

papaindigo · **Posted:** Fri Dec 06, 2013 10:45 am

GDE can check tune/no tune based on VIN # just email them.

CEL should be on with MAF unplugged and no tune assuming light is working. Switch key on but don't crank to check; if light cycles it's working; if it doesn't cycle invoke instrument cluster test by holding the trip odometer button while turning the ignition on. It will cycle through all bulbs and gauges.

If bulb is dead dealer will want $700+ not including labor for new cluster. Alternative pull cluster and replace $2 LED. I have how to if you email (not PM) me.

duncanm · **Joined:** Fri Dec 06, 2013 9:17 am **Posts:** 4

So...I just got off the phone with the dealership, the F37 recall was done on the vehicle a week before I bought it. So basically either the CEL bulb is bad or I am going to be competely lost....

kjjet · **Posted:** Fri Dec 06, 2013 11:12 am

dgeist wrote:

kjjet wrote:

The only way this could be is, your CRD has a MOD GDE or SERG. OR lamp is not operating?

KJJET

SEGR doesn't remove the need for a functional MAF sensor, it still takes in the values and passes them onto the ECM, just that it fakes the resistance on the feedback pin for the EGR accordingly with an analog step function based on input current. GDE tune is more likely, methinks. I'm guessing GDE could confirm if you pull the serial number on the case of the ECU and call them.

Dan

So... removing the MAF sensor with a SERG should still give you a CEL? Is that what your saying? I thought by removing the MAF the EGR was deactivated therefore giving you a CEL? But I see what your saying, even a bad MAF sensor should give you a CEL. But not with a GDE tune.

Any SERG users give confirmation on how it works?

Thanks
KJJET

kjjet · **Posted:** Fri Dec 06, 2013 11:17 am

duncanm...are you pulling the correct plug for the MAF sensor. There is a temp sensor also in the airbox. Just asking??

dgeist · **Posted:** Fri Dec 06, 2013 1:06 pm

kjjet wrote:

So... removing the MAF sensor with a SERG should still give you a CEL? Is that what your saying? I thought by removing the MAF the EGR was deactivated therefore giving you a CEL? But I see what your saying, even a bad MAF sensor should give you a CEL. But not with a GDE tune.
Any SERG users give confirmation on how it works?
KJJET

I am one...one of the oldest

It's a Synthetic EGR, meaning all the circuit does is pretend to be the EGR. The compuer likes the responses, so anything that an EGR would normally trigger (engine behaviors, codes, etc.) will be happily reported as a functioning device by the circuit.

The MAF sensor is used as an input to the function of the engine computer, so anything the computer is going to do in relation to the MAF, it should do it regardless of if you have the SEGR.

The presense of a GDE tune is the real question that should be answered, IMHO.

Dan

kjjet · **Posted:** Fri Dec 06, 2013 1:20 pm

Thanks for the information Dan!! Got it now.

duncanm · **Joined:** Fri Dec 06, 2013 9:17 am **Posts:** 4

Well guys...thanks for the help. My wife called me and said that the CEL came on, which is weird because I drove it for 30 minutes last night. Also confirmed that a GDE tune is not on the vehicle. Thanks for the insight.

CATCRD · **Posted:** Fri Dec 06, 2013 11:42 pm

When you pull the MAF the CEL will not come on until the second startup. All stock CRDs are like this.

kjjet · **Posted:** Fri Dec 06, 2013 11:47 pm

I'm glad you asked. I learned something about SERG systems.

Removing the MAF Sensor...no check engine light?

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