OBDII coder reader not working

[EdFree]

That may be a bit of a clue. Once it warms up it goes into closed loop mode and starts making adjustments based on the O2 sensors, etc. Just a thought, what about disconnecting the front O2 sensor to keep it in open loop and see how it runs when warm? Keep in mind you're going to set a code for the O2 sensor doing that, and will be unable to determine if it was already there from before since you're having trouble reading it now.... Down here some auto part stores will either scan for you or let you borrow the tool, anything similar there?

 

[JJacobs]

I see this kind of thing all the time. Usually it's on vehicles that power the DLC with the same fuse that runs the accessory power aka cig lighter. Regardless of what fuse it's on, if there is no power to the DLC then no scan tool will work. Check the wiring diagram for which pins are power and ground, it's standardized but I don't remember at the moment.

 

[hanaxj87]

Check your grounds . I had a similar problem with my son's 99 XJ .

Nothing would read the codes ,turned out the two ground wires that run to the plug was not hooked back up when the engine was replaced.

Both ground wires ran over to the same place and connected at the engine oil dipstick stud.. Look close because theres a alot of wires in the area and I missed the hanging wires at first.

Good Luck

Nick

 

[cdnabn49]

ok - did the off/on/off/on/off/on thing and GEN is displayed...

then the code I got was 1222 - MAP not grounded not sure if I am reading it correct... but does that mean I need a new MAP sensor?

so would that affect the MAP sensor ground reading as well?

 

[gradon]

The map wire might get its ground from the dipstick ground location as well. X2 on making sure all grounds are grounded, corrosion free, and tight(strap at firewall to head, battery to block below coil, and dipstick).

 

[cdnabn49]

cool will do... thank you to all y'all... will post results...

 

[cdnabn49]

ok, I only found 2 ground points; one on the battery and the other on the firewall attached to the rear of the engine...

 

[xj88superjeep]

Actually, the battery should have 2 grounds, one to the block at the dipstick, and one to the chassis at the fender near the battery tray. the third is block to firewall.

 

[cdnabn49]

can anyone post pic's of the grounds/locations for a 96 cherokee... also I have wire w/connector comming off the main wiring housing inside the engine bay not plugged in... not sure if it's supposed to.

you can also email them to me if ya can't post'em...

 

[gradon]

My 96 has the dipstick ground. There are 2-3 wires with rings on them that get grounded at that pt. Check this site to make sure you have power and ground at the obd2 connector: http://www.auterraweb.com/obdiipinout.html . If one is missing, then you can begin the trace. If both are there, then start suspecting the scanner.

 

[JJacobs]

Again- is there power to the DLC?

 

[cdnabn49]

sorry no reply, I have been fighting off the flu... figures on my days off I am sick but am better to go back to work...

 

[cdnabn49]

well you might have a communication issue due to a crapped out map sensor. do you have a volmeter and know how to use it???

start by unplugging the map sensor. if the 5v refernce is shorted the PCM will not communicate. if it communicates while unplugged you have found your problem but you need to check you wires first.

in no particular order/connector unplugged from map sensor/key on

wire 1 signal to PCM-no voltage when unplugged/no continuity to ground

wire 2 sensor ground-make sure you check for a good ground

wire 3 5v reference feed-make sure it has 5v or so, no continuity to ground

any problems on any of these wires could cause your problem, time for you to get to some diagnosing

ok, first 2 seem ok, last one reads from 5.09 - 1.53V fluctuates wildly and and somewhere close by is a "tick tick tick" silence tick tick tick" silence sound... not sure whats going on in there...

 

[cdnabn49]

I just read that not all 96 and 97 XJ's exported are completely OBDII compliant... ok question here is then why would I have an OBDII plug?

 

[xj88superjeep]

I just read that not all 96 and 97 XJ's exported are completely OBDII compliant... ok question here is then why would I have an OBDII plug?

They were OBDI before they switched to OBDII, and used the same plug.

 

[cdnabn49]

DOH!

 

[Matthew Currie]

They were OBDI before they switched to OBDII, and used the same plug.

Are you sure about this? I was under the impression that the OBDII plug is specific.

 

[xj88superjeep]

Are you sure about this? I was under the impression that the OBDII plug is specific.

then why would a code reader be OBD I AND OBD II compatible? CAN is not OBD II, but uses the same port. OBDI was not standardized, so maybe the port was different, but I thought it was the same port just different protocol.

 

[Blaine B.]

I thought all OBD2 ports were under the dash to the left side. That's how they all are now adays, I would guess that's how they were in 1996.

My 95's OBD1 plug is under the hood behind the PCM on the fenderwall.

I cannot get my OBD1 to read with an OBD1/2 reader, but have heard various others saying the same thing about their OBD1. I can get it to flash the code sequence.

Never heard anybody having problems reading OBD2 with a scanner though.