2001 Grand CherokeeWorking on vehicle.Throwing a few codesRun smooth at stsrt up. Abo

[dlmrun2002]

Have been driving the Jeep by using Actron code to run System Evap Test which eliminates my stumble when system goes closed loop. Taking Jeep to a mechanic Monday. Not sure what he will find. Being a vintage car owner I know hot rodders run brand new Corvette motors in old rat rods and trick the computers. I heard a capacitor will drop voltage down on some wire connections. I know my feed from PCM to Evap pump is not right. It needs to go to ground after initial open loop test. This Jeep really sucks. Can't wait to sell it.

dlm

 

[dlmrun2002]

Spoke to mechanic today. He has same results as me. Doesn't know the answer yet either. We both were wondering if there is one sensor that could be pulling the system down once going off open loop. I am thinking still possible PCM which I might send out. I hate to invest over $125 to have it tested/ repaired when I am not sure that is even the problem.

dlm ny country

 

[JPNinPA]

Do you have a factory service manual? If not it's worth it.
It has many tests for each sensor that will save you $$$

If the mechanic had one he follow some tests to determine cause.

What state and city are you in?

Regards,
JPNinPA

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[dlmrun2002]

I'm in Carmel, NY

I got a download manual from FLEAbay. It helped some. Schematic helped me trace out the PCM wire to the evaporation pump feed from PCM which had continuity.
Also got this info..

POSSIBLE CAUSES
- Vehicle History and Service Bulletin Investigation
- Generator source circuit open
- Leak detection pump solenoid control circuit open
- LDP solenoid control circuit shorted to ground
- Leak detection pump
- Wiring Harness Intermittent
- Powertrain control module

 

[dlmrun2002]

So repair center I sent my PCM out to told me it wasn't't repairable due to water damage. I explained my scenario but was told the unit would crap out while being tested, They only charged me a small % of what I was paying for in servicing the PCM. So I just got another ordered which will flash my vin and odometer. Just waiting for delivery. I did take a look inside my PCM before shipping out and the seal seemed good and I couldn't see any damage inside. Oh well. The beat goes on..

dlm ny country

 

[JPNinPA]

Who did you send it to? Allcomputersources? I see many people use them. They have a decent reputation.

Water damage? Was your vehicle in a flood or many water crossings?


Regards,
JPNinPA

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[dlmrun2002]

So the Grand Cherokee Laredo is fixed...sort of. My problems with bad stumble coming off open loop and erratic codes flying all over the place were all because of a PCM that had water damage. Car runs fine without any help form code reader or running code reader evap test. I picked up a used PCM and had it flashed for my vin number. I am still getting a code relating to 02 sensor heaters. P0031 and P0051. Checked fuse 16.. all good. Swapped out ASD relay which shares power to 02 heaters no luck ...Yet. Trying to get this OBD Sh*t behind me so I can dump this vehicle.

dlm ny country

 

[JPNinPA]

OXYGEN SENSOR 2/1 UPSTREAM - BLACK 4 WAY

FUNCTION
1OR/DGFUSED AUTO SHUT DOWN RELAY OUTPUT
2BR/WTOXYGEN SENSOR 2/1 HEATER CONTROL
3BK/LBSENSOR GROUND
4LG/RDOXYGEN SENSOR 2/1 SIGNAL



Regards,
JPNinPA

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[JPNinPA]

Check the wiring for shorts and breaks. Check the fuses.
Check the ground to engine block.


Regards,
JPNinPA

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[dlmrun2002]

Thanks for the pinout info...

I've been through the grounds in my journey the last 2 moths. Just did a check on fuse 16.

Swapped out ASD relay( carries power to 02 heater) just in case. I thought the pinout on the o2 sensor had two white wires for the heaters..no????


dlm ny country

 

[JPNinPA]

Lemme validate.


Regards,
JPNinPA

Sent using TapTalk

 

[JPNinPA]

I did not expect the PCM.


Looking at a few vendors the wire colors vary. Regardless of color the pin out is what matters.


Found this along the way

Check for excessive heat from exhaust melting the harness by the 02 sensor

Ignition on, engine not running.
With the scan tool, read DTCs
NOTE: If P0136 is set with the P0031 or P0051, inspect the related fused and
repair as necessary.
With the scan tool, actuate the O2 Heater test.
Monitor the O2 Heater Voltage for 5 minutes.
Did the voltage drop down close to zero during the Heater test?
Yes The conditions to set this code are not currently present
No Go To 2NOTE: Stop the actuation before continuing.

2
Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Measure the resistance of the O2 Heater Element at the O2 Sensor connector
(component side).
The resistance value for a 4.0L O2 Heater element is 4.0 to 5.0 ohms at 70°F
NOTE: The resistance value will increase with warmer temperatures.
Is the resistance within the listed specifications?
Yes Go To 3
No Replace the O2 Sensor.

3
Ignition on, engine not running, and the Sensor harness connector still disconnected.
With the scan tool, actuate the O2 Heater Test.
Using a 12-volt test light connected to ground, check for voltage on the Fused
ASD Relay Output in the O2 Sensor harness connector.
Does the test light illuminate brightly?
Yes Go To 4
No Repair the open or short to ground in the Fused ASD
Relay/O2 Heater Supply circuit. Inspect the related fuse and repair as necessary.
NOTE: Stop the actuation before continuing.

4
Turn the ignition off.
Disconnect the PCM harness connectors.
Measure the resistance of the O2 Heater Control circuit (PWM) from the O2 Sensor
harness connector to the PCM harness connector.
Is the resistance below 5.0 ohms?
Yes Go To 5
No Repair the excessive resistance in the PWM Heater Control circuit.
5
Measure the resistance between ground and the O2 Heater Control (PWM) circuit at
the O2 Sensor harness connector.
Is the resistance below 100 ohms?
Yes Repair the short to ground in the Heater Control (PWM) circuit.
No Go To 6

6
NOTE: Before continuing, check the PCM harness connector terminals for
corrosion, damage, or terminal push out. Repair as necessary.
inspect the wire harness and connectors. Pay
particular attention to all Power and Ground circuits.
If there are no possible causes remaining
Replace and program the Power train Control Module
P0080 does not show as a valid code in any of my reference material
Be sure to check the build date before doing all of this, if it is an early build a software update may fix your concern without doing all of this, the normal charge for a software update is 1 hours labor

Regards,
JPNinPA

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[dlmrun2002]

After some o2 testing my diagnosis was a faulty o2 sensor. Replaced the 1/1 o2 sensor with a NTK and at the moment my Grand Cherokee is running normal with no codes. I will give the system some legs this week, clear the monitors, get an inspection and sell this lump. It's not really a lump, but it's a car that was given to me and I never wanted. I would swap for a Wrangler maybe. After all this OBD crap it is time to move on to another BMW most likely. Big thanks to JPNinPA ...
You've been a great help along the way.

dlm ny country

 

[dlmrun2002]

Oh Snap... P0031 just came back. Car was fine sitting in driveway after 02 install idling for 15 minutes. Took car out for run and then code popped backup..Arggghh.. This Jeep.

dlm ny country

 

[JPNinPA]

Check fuse, ASD relay and wiring including reseating PCM connections.
Also verify you don't have an exhaust leak before the sensor.

Regards,
JPNinPA

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[dlmrun2002]

Swapped out a relay. Fuse good. No change. Cleared codes. Light lit up. Did a 50 mile run. Cleared codes. For 3 days know and over 150 miles no codes.. Yaaa!! Gonna park Jeep, schedule an inspection this week and sell sell sell this bad boy.

dlm ny country....

 

[dlmrun2002]

After one fail on inspection I finally got Jeep inspected. Vehicle runs fine with new(used) PCM. Took over 2 months to get this Grand Cherokee figured out. It is for sale at this point. Runs great but after driving BMW's since the mid 80's the design and engineering in this vehicle is real garbage. The quality of simple things like cruise control or even the mirrors is very low level. Now I know why I never even wanted this vehicle given to me in the first place. Time to turn the page.

dlm ny country

 

[JPNinPA]

Hmmm
Ya know you are dissing a Jeep on a forum made for jeep enthusiasts and jeep lovers? Most here don't worry about the luxury items as they want a capable off-road vehicle from a company noted for making some of the best inexpensive highly modifiable off-road vehicles. Plus every vehicles has a troublesome area.

Were you looking to sell it here? These is a section for that.
Glad you got it fixed and good luck on the sale.


Regards,
JPNinPA

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[dlmrun2002]

Yeah I know dissing the Jeep on a Jeep forum is a no no. I actually driver older BMW's. Can't afford the new stuff. I loved my YJ Wrangler. It's not luxury items either. Funny I mentioned cruise control and mirrors in my last post. I NEVER use cruise control. I needed to use it on my Jeep to clear the Cat Mon by running continuous speed of 35-40 mph for a few miles. Got that data from "Alldata" site and the guy who did my inspection. Maybe it's just a bad taste from this one car. Runs good now... 4 sale..


dlm ny country