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Unread 11-12-2006, 09:45 PM   #1
lbrty9
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1999 WJ 
 
Join Date: Apr 2002
Location: Hampton, VA
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MAP High Voltage - P0108

I'm getting an intermittent P0108 code. IT'll show up and then the check engine will go out for a while (several days to several weeeks). It did die on me the other day and threw this code as well.

I'm considering having the dealer diagnose this, but the check engine light isn't currently on and I'm not sure if the code needs to be continuous or not.

Any ideas? I'd had to shuck out $150 for a sensor I don't need, I'd hate even more to replace a PCM I don't need!

99 WJ with 4.7.

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Unread 11-13-2006, 07:15 AM   #2
greasefingers
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MAP Sensor Testing
Remove the connector at the MAP. There are three pins inside the connector (in a straight line). With the Key positioned to “On”and not start, you should see 5 volts across the outer two pins. This means that the PCM and wiring harness is good.

Reconnect the MAP sensor. Back-probe (with a paper clip) the center pin and connect the other end of the voltmeter to ground. With the ignition key On and the engine not running the voltage be 4 to 5 volts. Start the engine. The MAP should measure sometime 1 to 2 volts. Now open the throttle a bit and the voltage should increase with increasing rpms.
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Unread 11-13-2006, 08:47 AM   #3
lbrty9
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Thanks, that helps a LOT!!!
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99 GC, 4.7, 6" Clayton's LA, 315/75/R16's, FIPK, 3 inch Kolak exhaust, VIAIR 450 OBA, front ARB with Warn HS9500, Kevin's Sliderz, full skids, SURCO, Hi-Lift, Xenon's with Kolak harness, more to follow.
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Unread 11-13-2006, 02:29 PM   #4
GreenDean
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If you are getting a constant 5 volts threw the center pin AND/OR you get no reading across the two outters, you have a bad ground.
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Unread 09-04-2010, 02:23 PM   #5
maro35089
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i did this test and the center pin is runnig -1 to -2v does that mean its bad. that is with the engine running. with the engine off and in the on position its reading 4.3v bad sensor??
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Unread 09-04-2010, 04:58 PM   #6
rm2001wj
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One of the 3 pins is a ground and the other 2 have a positive voltage that is measured with respect to ground. Do the measurements again, but this time connect the negative probe of the voltmeter to some point (metal) on the engine or body, and then measure the voltage, with the positive probe, at each of the 3 pins separately. One of the outer pins should have zero volts (that's the ground) while the other should be at about 5 volts. The center pin will have a positive voltage this time.
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Unread 07-05-2011, 10:06 PM   #7
reeldagg
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P0108 - MAP Sensor - Jeep

I've had the same issue(s) with my 99 Jeep Grand Cherokee 4.7L. I had the wiring redone for the MAP sensor, the problem returned, replaced the sensor - still no joy. I suspect my problems are/were not related to the sensor, but the catalytic converter being blocked - so I've just replaced the cat. So far I have driven about 500km without any of the issues returning ( will let you know if they do). I reckon if I get to about 1500km driving without this P0108 happening I can say the problem is solved.

This is what I was experiencing
- Stalls while driving (just stopping dead)
- Slight surging at idle between 500rpm and 1000rpm
- Sudden shudder on open road while driving at 100kmph.
- Regular P0108.

What made me think it was a blocked cat ?
- Stalling is one of the symptoms
- I'd fixed the MAP sensor and I didn't want to believe it was the PCM.
- Surging
- The car has done 200,000 km and cats do wear out over time apparently.
- When starting up cold you could hear a bit of a hiss from the exhaust that wasn't there when the car was warm, cats apparently warm up and expand to allow the gas to pass through. If you cat is getting blocked you might notice this sort of noise.

I realise the original post is an old one - but hopefully my experience can help someone else.

Last edited by reeldagg; 07-05-2011 at 10:27 PM..
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Unread 07-08-2011, 06:45 AM   #8
reeldagg
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problem returned

Last edited by reeldagg; 07-08-2011 at 07:01 AM..
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Unread 10-12-2011, 11:56 PM   #9
badnunik
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I'm having the same issue, has anyone solved this problem yet?
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Unread 10-13-2011, 05:46 AM   #10
coralman
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Hiss=exhaust or manifold leak?
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Unread 11-18-2013, 06:44 PM   #11
Blakes10
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1999 Grand Cherokee

I just found this site, but have experienced the same Diagnostic Code. What concerns me is driving the car. On recent occasions, but at speeds of less than 20 MPH, partial electrical failure has occurred, causing loss of power steering and power boost on the brakes, along with misc items on the dash. The engine continues to run.

Is there a connection, you think, between the electrical failure and the P0108 Code? Thanks. Bill B
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