On Thu, 29 Jan 2004 20:35:49 -0600, Lawrence Glickman
|On Thu, 29 Jan 2004 20:26:27 -0600, Lawrence Glickman
||On Thu, 29 Jan 2004 20:07:02 -0600, Lawrence Glickman
|||On Fri, 30 Jan 2004 16:42:21 -0600, you wrote:
||||hi my code is 171&172 thanks for your help!!!
|||Whatever is measuring your lean/rich fuel mix is F.U.B.A.R.
||Heated Oxygen Sensor (two in some vehicles) upstream, 1 downstream
||after catalytic converter.
||One of the *inputs* to the Powertrain Control Module (PCM) that
||adjusts short term and long term fuel trim.
||ONE of the inputs to the PCM.
|=================================================|This monitor runs several tests by evaluating data from the heater
|circuit reference signals from each sensor. The upstream
|(precatalyst) HO2S monitor checks for high and low threshold voltage
|and switching frequency. Switching frequency, or cross-counts, is the
|number of times the signal voltage crosses the midpoint of the sensor
|signal range during a specific time. An HO2S monitor also evaluates
|sensor response by measuring the time required to perform a
|lean-torich and a rich-to-lean transition.
|The PCM compares test results to previously stored values. Because
|downstream (postcatalyst) O2S voltage fluctuations are slight and the
|signal seldom crosses the midpoint of the range, the monitor samples
|voltage level under lean and rich operation.
|During rich running conditions, the monitor looks for a fixed, low
|voltage signal from the downstream sensor.
|During lean conditions, the monitor looks for downstream HO2S voltage
|to stay high and steady. The diagnostic executive lights the mIL to
|alert the driver of a malfunction if an HO2s monitor fails on two
|Check the wiring to your O2 sensors, Dale. And maybe the O2 sensors
|themselves. There is a diagnostic procedure for this.
|||P0171 for your vehicle is: System too Lean ( Bank 1)
|||P0172 for your vehicle is: System too Rich ( Bank 1 )
|||So, there is your answer. The sensor is defective. The fuel mix
|||sensor for bank 1, or the wiring for it, or the connector for the
|||wiring, and so forth.
My guess is you have 2 upstream HO2S sensors, one for Bank 1
one for Bank 2
Your Bank 1 HO2S is hosed somehow.
|||Your computer is saying the light is ON -and- the light is OFF both at
|||the same time ( impossible ).
|||I don't have the repair manual for your vehicle. But you can get
|||information ( for a FEE $$$ ) at
||||----- Original Message -----
||||Sent: Tuesday, January 13, 2004 6:34 PM
||||Subject: Re: 1999 ford explorer idles rough when cold
||||> |When its cold (below 40 degress) my explorer will idle rough for a
||||> |so, then it idles normal. I checked my fuel pressure and it is at 59 psi
||||> |when it should be running between 35 to 45psi.When i pulled the vaccum
||||> |off the fuel pulse dampner the fuel pressure stayed the same. It is
||||> |a code saying that it is lean or rich conditions on bank 1 and bank 2. My
||||> |question would be is what could be causing this to happen?
||||> |I have changed the mass air sensor,the throttle positioning sensor,the
||||> |control sensor,the fuel pulse dampner,fuel filter,new plugs and plug
||||> |wiresand oxygen sensors.help!!!!
||||> Shotgun troubleshooting technique? No good. You can rebuild a car
||||> and not lose the alarm code. BTW, what IS the code? What is the
||||> OBDII code you're getting from your on-board computer?