I have a 2003 Expedition, 4.6. 4wd I read my trouble codes with my handy dandy Auto Zone Pocket Scanner and it gave me 8 codes. PO132,PO135, PO155, P2196, PO171, PO174, PO302, PO300. Can anyone decypher these for me? I would very much appreciate it. Thanks.

 

Load this page and scroll down to see most any code and what it means...
OBD-II Check Engine Light Trouble Codes

 

ok thanks alot

 

One thing you need to know about that many codes is that one part can be causing it. You have a cylinder 2 missfire code and multiple cylinder missfire code. P2196 is a "rich" oxygen sensor code. Makes sense with the missfire codes. Not firing means unburned fuel and could trigger o2 sensor. Other codes are lean oxygen sensor readings. Something is messed up. I could be spark plugs, the COPs. Doubt the 0xygen sensors are bad. They are just getting screwed up and adding codes to the list. How does the truck run? Does it have miss, underpowered, kind of feel like it chugs when you step on the gas especially in 3rd or 4th gear. Can you smell unburned fuel at the exhaust pipe.

 

Exactly. Start with that first code - the P0132. The PCM sets that code if see a voltage over 1.5 volts on the signal return line of the HO2S11 (first sensor on the bank 1 side) circuit. Normally the HO2S voltage should swing between .2v to .9v. If its over 1.5 volts the sensor circuit is shorted to either VPWR or VREF. (It could be shorted to the heater circuit of the HO2S.)

If the PCM can't trust the HO2S it has to guess at how much fuel to squirt. If it can't get it right and it is too rich or too lean a mixture it will cause misfires.

Just as a point of reference, unburned fuel won't trigger an O2 sensor code. Since it is an 'oxygen' sensor, the misfire will have unburned oxygen in the exhaust and the oxygen sensor will interpret that as a lean mixture, which could cause all the other lean codes. That will make the PCM drive the injectors full rich to compensate for for the excess oxygen and end up causing the P2196 code.

Time to break out the DVM . . . ..

 

I have heard before that one problem can cause multiple codes. It is underpowered by quite a bit and it does have a miss in it. I'll check it further this week and let you know what I find. Thanks again for all your help.

 

I think your problem lies with the spark plugs and/or cops. The cops are notorious for going bad. Since they are fairly inexpensive to replace now, you might want to start with that. You know No. 2 cylinder was tripping a code along multiple others. When was the last time you had a tune up done? How many miles on it? If these are unknown, then start there.

 

I changed the plugs in it last summer. But have recently found out that the ones I got from Auto Zone may not meet factory specs as I understand it. So that may be a big part of the problem right there. I also found out that one of the 02 sensors I put in last summer some how the wire got up against the cat and melted and shorted out. So thats not helping things either. Its got 125k miles on it so I am sure the cops need replacing too they are originals. Thanks for the advice it got me started looking and I found out lots of stuff. I think I am on the right track now.

 

Fix the o2 sensor or replace it, clear the codes and see what comes back. You know you have an o2 sensor that isn't working since you said the wiring is bad. That would be the first step. That may eliminate a few codes. Then see what is left and go from there.