Holy misinformation.

Yes, by definition, the Check Engine Light refers to emissions... so ALL CEL codes are emissions related.

There are several different categories of codes. A Readiness Monitor oversees each group (ie Misfire codes, Catalyst codes, Evap codes, etc). A typical car has 8-10 Readiness Monitors.
Not all codes are directly engine related, but since the engine makes most of the emissions on a vehicle, well... you do the math.

With me so far?

The tricky thing about check engine light codes (or more accurately DTCs - Diagnostic Trouble Codes) is... pay attention... they don't tell you what's wrong. Honest. What they tell you, in a nutshell, is what sensor saw something wrong. Sometimes the code description will give you a pretty good clue, but it can just as often be really misleading. It's a pretty stupid system.
The question now becomes, WHY was that code set? What is the actual problem? Well, like most car repairs, go diagnose it, and fix it. The DTC is a symptom. Not the problem.

A very common example of this is an oxygen sensor code. There are quite a few different O2 codes, but just because you have an O2 code, doesn't mean you need an oxygen sensor. Could be plugs, or a fuel filter, or a catalytic converter, or yes, possibly an O2 sensor. But, too many people (mechanics included) see an O2 code, install an oxygen sensor, and still have a check engine light. D'oh.

Long Term Fuel B1 System Too Lean means the air/fuel ratio is too lean. Period. (This code is kinda tricky- the fuel trim is too lean because the PCM commanded the fuel injection to run lean to compensate for a rich condition. The engine is actually running rich. Did I mention OBD is a really dumb system?)
Long Term Fuel B1 System Too Lean doesn't mean the MAF sensor is bad, or an O2 is bad, or you need a tune up, or smoking is bad for you. Sure, MAF sensors are a common cause of this code on VWs, but not the only one.

I totally forgot my point.

But it's almost never as simple as 'Pxxx code = such and such repair'.

And never believe what you read on the internet. So ignore everything I said.

 

I've read enough to know that VW and CEL is synonymous so I shouldn't be surprised. Here goes my events and what all I've done about it.

2001 VW Jetta GLS 2.8L VR6
I've gotten the too rich too lean code for years. I replaced the MAF a few years ago and it did go away. It's been back a few times and I've just kept clearing the code long enough to get emissions done and been on my way.

I had a few things that needed replacing as I drove the car across country (it did great) and finally decided to fix this thing as much as I can.

A year ago, had a new AC compressor/clutch, serpentine belt put in.

A couple weeks ago I changed the front fan motors, axillary water pump, alternator, plugs, plug wires, fuel injection cleaner, cabin filter, air filter.

The other day the EPC light and traction control light came on to accompany the CEL that had been on forever.

I ran the diagnostics and got 4 codes today:
P1128
P1142
P0101
P1137

Today I changed to synthetic oil, changed the fuel filter, pre and post 02 sensors. Codes were cleared before fixing the 02 sensors, fuel filter and oil change. Drove it for 60 miles, they didn't come back on.

Took the throttle body off and cleaned out the carbon residue, put it all back together, car drove amazing better with more power but the CEL came back on after about 5 miles.

I was pretty certain the throttle body gasket was worn and the cause of a vacuum leak and it might have been but evidently something else is tripping the CEL. Any thoughts after sharing all of that?

Appreciate it!

 

I just had this problem while driving across the country. After the CEL came on, my '98 Jetta's fuel efficiency became terrible. I figured it was some silly sensor, but I had no way to know for sure. But I was poking around in the engine while at my motel, and noticed a old degraded rubber hose that was torn. I was going to duct-tape it and see if that helped, but fortunately a local guy (who happened to be a mechanic) came by, stuck a code reader thing on it, and got p1128. He said that was probably some vacuum problem, and I mentioned the torn hose I found. He pulled some hose off an old junk truck at his shop and replaced the torn one (the part wasn't in stock in the area).

I'll know for sure if that was the problem or not tomorrow when I head back out on the road. I sure am grateful to that guy.

 

While going through net i found that in VW P1128 specifies a Long Term Fuel Trim - System Too Lean Bank 1? What does that actually mean and specify.

 

I have a question because i have a 1999 jetta gls with 85,000 and one day i was driving and the check engine light came on so I took my car to autozone they told me it was this code P1128 so i dont know if its the MAF sensor or what did you replace it or what happen?

 

P1128 was just one of several codes present when my step mom gave me her 01 GLS new beetle (2.0 ltr 1984 cc AEG motor). My first impression based simply on the description was un-metered air was entering the system by means of a cracked vacuum line/hose. I ended up having to replace the up-stream air fuel 02 sensor (based on P0342 code), the Mass Air Flow sensor (just because I had read so many forums about the MAF going bad and I noticed a 10 mpg drop in performance) and eventually ended up with a linguiring P1128. I don't know yet but I did find the vacuum line from the manifold to the FPR (fuel pressure regulator) had completely rotted in two. Less than a dollar spent at Advance Auto for a short piece of vacuum hose and I am now waiting to get my hands on an ODBII scanner to reset the MIL and verify the performance level of sensors. If nothing else I will simply use the negative battery terminal trick and hope that in a week nothing else trips the MIL. In that case I will consider it case closed for the P1128 code. I realize this conversation is ancient but never the less it may prove helpful for someone just browsing for a fix.

 

Welcome to the forum.


It appears you brought up an old thread.