hello to all.
I have a 1996 ford f150. 4.9l just replace all 3 02 sensors, codes for all 3 were set. replaced with bosch and the code for bank2 sensor 1 heater malfunction came back on. replaced with another 02 sensor and cleared codes. light for bank2 sensor 1 heater malfunction came back on. has anyone had this happen before? is it just faulty sensors or doen ford computer need flash programing? not sure where to go next.

thanks for any help popssible.
TC
tc5210@yahoo.com

 

sound like you may have a problem with the wiring or the plug going to the sensor. check make sure the wire is not nicked or freyed and the plug is not corroeded.
watch wre you are posting this, it would have been better suited in the proper F-150 forum.

 

Welcome to the site

Please read:

https://www.ford-trucks.com/forums/s...d.php?t=300691

 

Hmm, this concerns me I have the same truck (96 F-150, 4.9L I-6) and have been getting the same codes (171 and 174 (System too lean (Bank 1 (171) and Bank 2 (174)))).
I also too bought 3 new Bosch O2 sensors, but haven't installed them yet. The parts ruffian @ Autozone told me it could also be the MAF (Mass-Airflow Sensor - located next to the airbox on the inlet tube) sensor, of which I think can be checked with a multi-meter. I will be checking mine if it's possible Especially if installing all these new O2 sensors don't work!

 

Blaming the O2 sensors for "system too lean" is sometimes like blaming the scale for "you weigh too much", or blaming the mirror for "you don't look so good".

Ford MAF sensors are known for getting contaminated over time. As they get dirty, they tend to register too low for the air that is actually flowing. This will lean out the air/fuel ratio. The computer will use feedback from the O2 sensors to compensate, to a point. Eventually it hits the limit of how much it wishes to compensate, and it will flag Code 171/174, which means "System indicates too lean", not the typical Autozone interpretation of "Your O2 sensor is bad". You cannot test a MAF sensor with just a multi-meter, other than for complete loss of functionality.

Ford says you must replace the MAF sensor once it is dirty. However, people have found that you can clean the MAF sensor wire with electrical contact cleaner. Don't use brake cleaner. Do not touch the wire with anything. Disconnect the battery for 15 minutes after doing this, to force the computer to re-learn the MAF sensor transfer characteristics. (None of this applies to the MAP sensors found in most of the trucks in this section).

It is possible that both oxygen sensors have gone bad at the same time. But it is more likely that a common "lean mixture" condition is causing them to accurately indicate what the engine is doing, and brand new sensors will/should do the same thing.

Other things can cause lean codes. Vacuum leaks, induction system leaks, low fuel pressure are examples.

A "heater circuit malfunction" probably means that 12 volts is not reaching the heater circuit on the sensor, or that the computer doesn't think it is. This can be bad wiring, fried fusible link, or corroded connections. It is not likely to be a bad sensor.

 

Damn, that's some kick azz freaking information there!

So what you are saying if I read correctly ("clean the MAF sensor wire with electrical contact cleaner" and "Do not touch the wire with anything"), is that one should use the electrical contact cleaner (i think you mean the spray can stuff used for cleaning potentiometers and stuff) and spray the sensor wire with the mist, but don't touch it, even with a soft clean shop towel with the contact cleaner on it?
Just really curious, as I will be trying this in 4hrs

 

Yes, spritz the fine wire with the spray but DO NOT TOUCH IT WITH ANYTHING. The wire is very, very fragile.

Take a look at the Explorer board, this is discussed in a "sticky" at the top. I gave my Explorer this treatment and it did seem to help.

 

Cool As I have this problem, and I believe I have some of this cleaner already, I'll attempt this job tonight ....as well as spraying TB cleaner at all my vacuum hoses looking for leaks.

 

Uh, pardon me for taking issue with your glittering generalities regarding my fellow AutoZoners:

Every AZ store has a section in it's parts look-up computers that aid in the interpretation of MIL codes. Also available to the Zoner is a small flip-page notebook with the MIL codes and their auto industry approved definitions. AZ also tests it's Zoners in proficiency in MIL interpretation. It's not like we're a bunch of untrained monkeys running around with a scan-tool...

The issue is more the willingness of most customers to simply start replacing parts *****-nilly instead of taking the time (or the vehicle to a mechanic) to diagnose the problem correctly (loose/dirty connections, broken wires, etc). Codes 171 and 174 (fuel trim condition, banks 1 and 2) set together do indeed indicate a problem with the MAF - or a vacuum leak, a misfire condition or a fuel pressure problem. Which one is it? Diagnose it, don't just throw parts at it. I always tell the customer that I can't do a diagnosis simply by throwing the scan-tool on it, you have to get into it and see what the underlying cause is. Sometimes it's something as simple as a connection problem, a split vacuum hose or a plugged fuel filter, sometimes it's a bad - or simply dirty - MAF. And the first thing the customer who just starts throwing parts at a problem says when the light stays on after they "fix" their car themselves? "You told me that is was the (insert part name here)." No, we told you it MIGHT be that, but it also MIGHT be something else, and you need to get it looked at by a shop to be sure which it is.

A full and groveling apology is expected, knave.

 

Whoa Dude!!! I'm not even involved in this one and I have this overwhelming urge to publicly apologize to every parts counter worker that I've ever flamed in my entire life!

Cheers!

Mike

 

Sorry to go against the grain Dad's but at my AZ, the newb gets to do the code readings so bad first advice is not uncommon. I will however state for the record that Kelly, at my store, is simply awesome!

 

OK, I will take fault for purchasing O2 sensors without properly diagnosing the problem, I did read that they are wear items, so it wouldn't hurt to replace them anyways.

What I will take issue with is AZ part's database system! :P It stated my truck only required 1 before-cat O2 sensor, and not 2. I watched at the parts guy navigated through the selections to enter my truck information into the program, and it was all correct. I asked the parts guy to make sure, and he said that if it required two, the system would put a message under the part's description stating the vehicle requires 2 .

 

Roushians, how did you make out?

 

While we're waiting for his answer, I'll tell you that my mileage improved from 14-15 to nearly 18 by replacing mine (5.0/E4OD). On the rear tank, anyway. I have a rather sizable fuel leak in the front tank/line, apparently. That one is still at 14-15. I need to investigate that...

 

Replacing your what? O2 Sensors?


My Update: I disassembled and cleaned my MAF sensor using some good Loctite Electronics Control Cleaner spray. The MAF sensor looked pretty clean after removing it, and before cleaning it.
I have yet to install the O2 Sensors I've bought.
After cleaning the MAF sensor, I've noticed that I get the Bank 1 Lean code (171) pretty quickly after clearing the previous code out, much more quicker than before! (a few miles compared to a week or more).
I also tried the "spray carb/TB cleaner at subject vacuum line areas" vacuum leak technique, with no results. We'll see what happens, as I still have to install the O2 sensors, fuel filter, and having the fuel pressure checked.