View Full Version : Code "running lean bank 1 and 2"

04-12-2008, 02:04 AM
I bought an OBDii to check my SES codes. It comes up with "running lean bank 1 and 2". P0121 and 124

I am at a loss of what to do now. Replaced t-stat, CPS and a mechanic recommended the fuel filter and from my research on this site I am lead to believe that it may be the coolant temp sensor.

Problem: 2002 vue 6cyl.
SES: code Po121 and 124 "running lean bank 1 and 2"
fan running constantly even when ideling
coolant disapearing but no leaks detected
decreased gas mileage.

What next??? I plan on replacing the Coolant temp sensor in hopes that this stops the fan from running.:dizzy:

04-12-2008, 02:17 AM
i think you posted in the wrong area... anyways... dtc p0124 and p0121... well... its a 3.0 v6.. make sure that all the hoses are connected and not cracked causing unmetered air to enter the engine... has the car every had vacuum chamber springs installed??? there is a tsb about this dtc. it can be caused by air entering from underneath the vacuum reservior chamber under a decel causing the plate to lift up therefore letting unmetered air to enter the engine... this is your most likely cause!! although a skewed Mass air flow sensor can cause this issue to. if i were to guess i would buy the vacuum chamber springs from the dealer.. if you need PN respond.. take about 30 mins or so to change out and less than 50 bucks in parts... as far as your leak... any drops on the ground?? you could have a oil cooler plate leaking.. thats under the manifold and hard to inspect completely.. or a water pump leaking too.....GL

04-12-2008, 10:44 AM
You did post in the Sky forum and should have posted in the Vue area. Newbie mistake but whatever. You can ask the administrator to move these posts to the Vue forums if he isn't too busy manipulating all the knobs and dials behind the curtain(?). Think Wizard of...........:D

Your OBD II readout seems to differ from this library's code list in the How-to Tips page 5 titled OBD II Powertrain Codes;

DTC P0121 TP Sensor Circuit Insufficient Activity

DTC P0124 Throttle Position Sensor 1 Circuit Intermittent

My FSM, although only for the '02-'03 L200/L300 models, still shares the same V6 engine as yours so the DTC codes should be similar and match the above two codes. Perhaps you can have the codes read by another reader from an auto store to be sure there isn't any confusion going down the wrong road. Been there, done that.

If you find that the above codes are the correct ones then address the tps problem; loose connection or worn tps. Simply disconnecting and reconnecting the tps may solve the problem otherwise measuring the tps off the engine can sometimes reveal whether or not replacement is necessary by using a multimeter to measure for resistance in a linear mode.

The constant running fan may be a stuck fan relay; locating the relay in the engine fuse box, removing it and substituting it with a similar one nearby like the horn relay may help. If not and the fan continues running then it's most likely the coolant sensor although we have the newer brass ones in our engines. If the fan relay is causing the constantly running fan it may be the relay contacts sticking; rapping the relay against a hard surface (battery top, table, engine frame) will free the contacts. It can be re-used in the horn circuit or replaced altogether.

The decreased gas mileage, loss of coolant, and lean conditions (most likeley incorrect code) conflict as symptoms if the codes are correct. Losing gas mileage is more believeable than the codes so more information may be needed; what's the mileage, plugs replaced, air filter, oil, etc.? Looked carefully for coolant leaking past loose loose hose clamps, tiny cracks in the radiator (near the transmission lines), by the firewall inlet/outlet lines to the heater coil where the O-rings wear and eventually leak coolant into the interior, and lastly - coolant in the oil?

04-12-2008, 11:33 AM
Being a newbie how do I have this changed to the vue tech?

Also I posted the wrong codes. I was half asleep:sleep: last night.

The correct codes are PO171 and 174

sorry for the trouble.

04-12-2008, 02:20 PM
Asking the Administrator to move the threads - e-mail, wait and see.

No excuses for sleeping and posting misleading codes!? Do you have any idea how much I have to flap my wings flying from the How-to library to this forum!? :hmpf: I'm gonna' have to do some duck talkin' wit the Adminstrator 'bout dis..................................:xeye:

OK, forget the tps suggestions. This now seems to point to the mass air flow sensor (MAF). Read the posts, search the threads on maf symptoms as this is an expensive replacement item. Possibly trying a (temporary at best) cleaning of the maf sensor with the appropriate cleaner may help. Someone recommended CRC MAF sensor cleaner although I wonder if its just a relabeled can of electrical contact cleaner. For an eye opener on prices, check out the replacement costs in http://rockauto.com or http://saturnparts.net. BTW, saturnparts.net was brought up this week by a member asking why there seems to be a long wait period and no replies to e-mails or reasonable explanation for delayed shipping.

04-12-2008, 09:42 PM
i would recommend these vacuum chamber springs first.. pn is 93175463
trust me this will fix your problem

04-16-2008, 04:02 PM
I just replaced the Coolant temp sensor which after taken out and replaced the old one seemed fine. DAMN!:upset:

So my service wrench light came on with code po118 pd what does "pending" mean?

I cleared the codes and nothing has come up yet. The fan ran again right when I turned on the car but stopped and then it decided to idel (sp) funny for a min.:eek: It was like it wanted to burp or something and turn off. I let it go for a min to see if it would correct itself. But it didn't When I tapped the gas it stopped and ran normal. After replacing the tstat a few months back it was torqued to specifications from ssicarman post from 08-21-2005, 09:16 PM

Still have codes po 171 and 174 running lean bank 1 and 2!:x

I am heading out on Tuesday driving to so-cal (400 miles) for my sisters wedding and with the codes coming up I am thinking to rent a cheap little car, or can I drive it? I am thinking of giving up trying to fix it myself.:cry: Take it to a mechanic who will no doubt tell me what I already know and charge me my 1st born!


04-16-2008, 05:28 PM
P0118 ECT Sensor Circuit High Voltage/Low Temperature

This would explain the intermittent fan running on/off as the ECM thinks the engine is cold (-38F)!? An open caused by a poor/intermittent connection on the wiring can turn this DTC on and turn on the fans. Checking the connector for chafing, shorting, or fouling may result in this DTC.

DTC P0171 Fuel Trim System Lean Bank 1

DTC P0174 Fuel Trim System Lean Bank 2

As posted previously, these two together suggests a problem with the MAF sensor. The other possible causes are;
1-Vacuum leaks (intake manifold vacuum lines, upper and lower intake manifolds, intake manifold vacuum reservoir, and the power brake booster.

2-Fuel pressure low

3-Poor fuel quality or water in fuel

4-EGR valve stuck open

5-Coolant temperature skewed towards a higher temperature

6-MAF sensor signal voltage skewed low (causing a lean condition)

The above are from the FSM for the '02-'03 L300 V6 3.0L engine that we share.

04-17-2008, 01:18 AM
I reset the codes after the last post. My vue sounds great! :D the fan has yet to run on idel.

BUT... now I have po503pd:x:x:x
"Speed sensor a erratic/high"

Still running lean 1 and 2.

Is there a possibility that I messed up the speed sensor when replacing the coolant temp sensor?

The PO 118 is gone