lw300 brakes

My 2001 lw300 has been getting to require more brake pedal force to stop.
The traction control has also been shutting down and ses lamp is on. Haven't
read out the code yet ( haven't been able to borrow a reader just yet). I
reset the codes by pulling the fuse but they came back.

Front brakes were OK. Rear brakes were the problem.
The caliper is a dual piston, one on each side of the disc and the caliper
itself is a rigid mount. Using a drift, I pushed out the two pins that
secure the pads into the caliper and pulled out the keeper spring. The pads
should now be able to pull out, perhaps needing only the pistons to be
retracted slightly. Outboard pads on both rears were fine but the inboards
were solidly rusted in place. Took a bit of effort to break loose and
remove. Both had far less wear than the outboard shoes indicating that they
had rusted solid and were not functional at all. I removed the rust so that
there was a decent fit again and added a small (very small) dab of
never-seize to the tracks.

While I was at it, rotated the tires and replaced the fuel filter. Old
filter, you could hardly blow through.

So far, no ses and engine is running smooth (also did an oil change using a
5-minute engine flush) and brake pedal effort is back to normal.

 

Brakes are still fine now but last night noticed that the ses was on again
and the TRAC light was off. Right after that my friendly (fienldy?)
constable pulled me over for a brake light out. Was the usual crud with the
darn tail light design - the lamp holder was not making correct contact to
the base assembly. Just rocking the lamp holder slightly made the light come
on again. Until the recall is done on the tail light assemblies, I just tied
a string to one of the mounting studs and to the lamp holder to cock it
slightly inboard. Next engine start, the TRAC light came on again as normal.
Could be that there is some connection between a defective brake light and
the TRAC light. Neither the owner's manual or the service manual says this
though.

I borrowed a scan tool this morning to check if there were any stored codes.
I only checked the generic codes (should have done specific codes but would
take me an hour to figure how to get to them on this multi-kilobuck tool).
Got P0171 and P0174 System too lean bank 1 and bank 2 respectively. This may
be a vestige of the fuel filter I replaced the other day. My friend at the
garage said that it was most likely the MAF sensor or a vacuum leak. I
didn't hear any vacuum leaks so have to find the PCV line and check the
valve. The scanner indicated that the car is driveable so I cleared the
codes and will check again in a few days. The ses lamp had gone off by
itself on the way to the garage this morning. I have 67000miles on the car
now.

I hear the MAF sensor can be cleaned with brake cleaner or electrical
cleaner. It's delicate and expensive. Anybody have recommendations?

 

I believe the TRAC system is essentially part of the ABS system, so if there
is a fault in the ABS, maybe that is why the TRAC system goes down. Does it
turn on if you press the button? I am wondering if the rear brake lite is a
red herring and you actually have a fault in the ABS too. Brake sensors
clean?

--
Dana
Port Kent, NY

2002 Saturn LW300
93 Jeep YJ - I4 - 125k mi.
90 Jeep XJ Ltd. - I6 - 145k mi.

 

Initially, the light on the TRAC button went out by itself and could not be
turned on. It would come on for a couple of seconds at key-on and then go
off. I had pulled the controls B+ fuse to do a reset of any faults and the
TRAC light stayed on. It has gone out several times which is why I started
to look into the brakes. I did pull the rear brake sensor connectors and
re-seated. Did not pull the rear rotors to check the sensors.
When you ask, are the brake sensors clean, are you referring to the
connectors? Afik, the sensors are 'gear tooth' hall sensors...hmmm, now that
I think of it, the sensors are probably magnetically biased and might
attract rotor dust. Probably a good idea to pull the rotors and check.
Thanks.
Oppie
White Plains, NY

2001 LW300
Bicycle <grin>

 

I don't know about the Saturn specifically, but I'v recently had a crash
course in ABS-ology with my Jeep. The sensors can accumulate dust, both
ferrous and anything that can stick with humidity. Another thing to check is
to make sure the gaps are still in spec.

Dana

 

So far, so good. After clearing the codes with a professional tool - this
following changing the fuel filter an oil change, new tank of gas and fixing
the stuck rear brake pads - no new codes.
I put on 50 miles yesterday and expect to put on about 120 today. I'm
going on vacation Thursday and wanted to be sure that we don't get stuck.
Think that I'll pull the rotors when I get back just to have a look-see.
Oppie

 

Just got back from four days in the mountains of Vermont. Put on almost 500
miles and averaged close to 30mpg!
Got to love highway driving.
ABS/TRAC/Brakes were all great on the trip. No SES or anything until... I am
two miles from my house on the return trip. Read out the code this morning
and got 'Lean Bank #1' P0171. Did not also get the lean bank 2 as did a
couple of weeks ago.

Can anybody shed any light on how the car knows of a lean condition in one
bank? I don't especially care to run out and buy a new mass airflow sensor.
The vehicle is otherwise running nicely.

There should be a list out there somewhere that details the various engine
management strategies and the self diagnostic strategies. Would be helpful
in understanding any faults. Just like last summer when I got a 'evap
canister large leak', the last place I looked was the canister. I looked
first at the seal on the gas cap and then found the actual fault in the vent
solenoid that was stuck open... Now that I think of it, the service manual
has some data on this. Got some reading to do now.
Oppie

 

2001 Saturn L300/LW300
DTC P0171
Circuit Description

A closed loop air/fuel metering system is used to provide the best
combination of driveability, fuel economy, and emission control. In this
system, short term fuel control is accomplished by the ECM rapidly
responding to the oxygen sensor readings. These changes finely tune
engine fueling. The long term fuel trim control is determined by the
trends of the short term fuel trim. The ECM uses the long term fuel trim
to make course adjustments to the engine fueling. Under normal driving
conditions, except power enrichment mode, the ECM attempts to maintain a
14.7 to 1 air/fuel ratio. Fuel trim values of 0% are ideal. If the value
is above 0%, this indicates the engine is running lean. Therefore the
ECM commands more fuel to the system in attempt to maintain a 14.7 to 1
air/fuel ratio. If the value is below 0%, this indicates the engine is
running rich. Therefore the ECM commands less fuel to the system in
attempt to maintain a 14.7 to 1 air/fuel ratio. The ECM stores fuel trim
values for three different speed/load ranges: idle, medium speed/load,
and high speed/load. DTC P0171 will set if the long term fuel trim value
exceeds a calibrated upper level in any of the above described
speed/load ranges.
DTC Parameters

DTC P0171 will set if the vehicle is in closed loop and the following
fuel trim limits have been exceeded:

* Idle: 7.7%.
* Medium engine speed/load: 21%.
* High engine speed/load: 21%.

DTC P0171 diagnostic runs continuously once the above conditions have
been met.

P0171 is a (type B) DTC.
Diagnostic Aids

DTC P0171 indicates the engine is running lean. The following are
possible causes of a lean air/fuel mixture:

* Vacuum leak.
* Fuel pressure low.
* Fuel quality poor or water in fuel.
* Exhaust manifold gasket leak or leak around HO2S bank 1 sensor 1.
* Fuel injectors clogged.

To verify the system is running lean, use Scan tool to monitor HO2S BANK
1 SENSOR 1 and HO2S BANK 1 SENSOR 2. If HO2S bank 1 sensor 1 lambda
value is greater than 1.2 and HO2S bank 1 sensor 2 is below 300 mV, the
system is running lean and the oxygen sensors are probably not at fault.

 

That was a GREAT description. Thank You.
May I ask where you got that from? Similar information might be useful in
the future.
Oppie

<snip>

 

GM eSI disk of course. I got all 98-04 GM vehicles covered.

 

I was still getting the P0171/P0174 codes.
Pulled the MAF and sprayed down with cleaner. Checked fuel pressure which is
holding at 49psi, reset the codes and hope for the best again. Plenty of
torque at low speed but at high RPMs (3500 and up) the torque is not there.
I've got to check the fuel pressure under load. Found that my old R12 air
conditioning service gauge will fit the fuel pressure test port.

Noted that the TRAC light is a good precursor that the SES light is about to
go on. Evidently, when there are engine management issues, the Traction
Control system is shut down. This has been happening about 10 miles before
the SES comes on.