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All sensors throwing high voltage codes?

O

outlander

NAXJA Forum User
Location
Columbus,Ohio
What would cause all sensors to throw those codes at the same time?
Where should i start diagnosis...short somewhere?
This is not on my xj but my 97 grand cherokee 4.0
Thanks.
 
Start with a physical inspection of the wire harnesses, including all the way to the O2 sensors.
 
All this started after i was using my dvm to check my sensors.
I question this procedure wich uses battery pos to check ground;
(Quote from this site;http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-map-sensor-2)
With your multimeter still in Volts DC mode from the previous test and the Key On (but engine Off).

Probe the wire labeled with the number 3 in the image viewer, with the BLACK multimeter lead.

It doesn't matter if you probe this circuit (wire) with the connector connected to the MAP sensor or not, but do not probe the front of the connector (if you decide to unplug the connector to test for this path to ground).
3
Now connect the multimeter's RED test lead on the battery's positive (+) post.
4
Your multimeter should show you either:

1.) 12 Volts DC

2.) 0 Volts.
(End quote)
 
I got a 12 volt reading but just sounds counter intuitive to hook a dvm up to batt pos. And hook other lead up to the sensor ground to check for good ground?
Wouldnt this send 12 volts through the pcms sensor ground circuit?
(The pcm is responsible for applying ground to sensors)
 
Bad, poor, dirty loose ground(s). Or short like already suggested. I'll bet on a burned up or loose, dirty main sensor grounds
 
Last edited:
That procedure is correct, but is not the way I do it. I have used that method on a rare occasion.

outlander said:
All this started after i was using my dvm to check my sensors.
I question this procedure wich uses battery pos to check ground;
(Quote from this site;http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-map-sensor-2)
With your multimeter still in Volts DC mode from the previous test and the Key On (but engine Off).

Probe the wire labeled with the number 3 in the image viewer, with the BLACK multimeter lead.

It doesn't matter if you probe this circuit (wire) with the connector connected to the MAP sensor or not, but do not probe the front of the connector (if you decide to unplug the connector to test for this path to ground).
3
Now connect the multimeter's RED test lead on the battery's positive (+) post.
4
Your multimeter should show you either:

1.) 12 Volts DC

2.) 0 Volts.
(End quote)
Click to expand...
 
outlander said:
I got a 12 volt reading but just sounds counter intuitive to hook a dvm up to batt pos. And hook other lead up to the sensor ground to check for good ground?
Wouldnt this send 12 volts through the pcms sensor ground circuit?
(The pcm is responsible for applying ground to sensors)
Click to expand...

If the ground was bad and the MAP was shorted to the PCM, then yes. That is why I do not use that method. It is good for checking back voltage on a starter ground.
 
outlander said:
I got a 12 volt reading but just sounds counter intuitive to hook a dvm up to batt pos. And hook other lead up to the sensor ground to check for good ground?
Wouldnt this send 12 volts through the pcms sensor ground circuit?
(The pcm is responsible for applying ground to sensors)
Click to expand...


YES.
 
I wonder if the pcm got confused by seeing 12 volts on its sensor ground circuit and caused it to throw voltage high codes for all the sensors?
Maybe ill get my brothers scanner and erase the code and see if it returns...
 
Sounds like a plan.
 
outlander said:
So did i fry my pcm by doing that test method you think?
Cel came on after the test i did.
Click to expand...

Was the power on or engine running during the test? You should have run that test with the power off.
 
Originally Posted by outlander View Post

I got a 12 volt reading but just sounds counter intuitive to hook a dvm up to batt pos. And hook other lead up to the sensor ground to check for good ground?
Wouldnt this send 12 volts through the pcms sensor ground circuit?
(The pcm is responsible for applying ground to sensors)
Click to expand...

The answer is NO. If you were really in the voltmeter mode, the impedance from the Battery + to where you probed, caused by the meter would be in the tens of megohm's.
 
old_man said:
Originally Posted by outlander View Post



The answer is NO. If you were really in the voltmeter mode, the impedance from the Battery + to where you probed, caused by the meter would be in the tens of megohm's.
Click to expand...
I was in 12 volt dc mode with a craftsman auto ranging high impedance dvmm (no low end crap)
 
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