O2 sensor help

Closed Thread Subscribe

Thread Tools

Search this Thread

08-10-2011, 11:19 AM

ZR2Daddy01

New Member

Thread Starter

Join Date: Apr 2010

Location: Liverpool NY

Posts: 65

O2 sensor help

I have a 2001 blazer and this 02 sensor problem has me stumped and I can't find an answer anywhere. so here's how it started I had a p0141 code come up on and off for the first two years I had the blazer. Finally the ses light wouldn't shut off so I replaced the sensor ses light goes out no problem. Couple weeks later ses light is back on but this time it's p0140 showing no circut activity, checked wiring harness, voltage etc everythings ok light goes out on it's own. Light comes back on and stays on for some time so I go through it all again, goes out and comes back on a couple days later. Now this morning on my way to work the light goes out so I scanned it and it still shows p0140 as an active code but tells me the ses light souls be off when running. Now I need someone to hopefully point me in the right direction cause I've run outta ideas and can't seem to find an answer.

08-10-2011, 11:38 AM

swartlkk

Administrator

Join Date: May 2005

Location: Waterloo, NY

Posts: 41,151

The typical OBD2 description for each of these codes is:
P0140 - HO2S Circuit Insufficient Activity Bank 1 Sensor 2
P0141 - HO2S Heater Circuit Bank 1 Sensor 2

However, the 2001 reference I have calls them:
P0140 - HO2S Voltage within Bias Range - HO2S voltage is steady between 400-475 mV for 150 seconds
P0141 - HO2S Voltage stays within 150mV of Startup Voltage - Pretty self explanatory. The length of time for this code depends on the engine coolant temp & airflow through the MAF.

Combining these two code descriptions, it would seem that there may be a wiring issue with your B1S2 sensor. You basically have to look at the sensors using a scan tool and step down through the diagnosis. If you have access to a scan tool capable of displaying the O2 sensor output voltages, I can supply the diagnostic steps.

*EDIT*

Quote:

DTC P0140: HEATED OXYGEN SENSOR VOLTAGE IS WITHIN BIAS RANGE

Circuit Description

NOTE: For circuit reference, see WIRING DIAGRAMS article. CHECK under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.

Heated Oxygen Sensor (HO2S) is designed to create a voltage relative to oxygen content in engine exhaust stream. The control module supplies HO2S with signal high and low circuits. Ignition voltage and ground are supplied to HO2S heater by independent circuits. The oxygen content of exhaust indicates when engine is operating lean or rich. When HO2S detects that engine is operating rich, the signal voltage is high, and decreases the signal voltage as engine runs leaner. This oscillation is sometimes referred to as activity or switching, can be monitored with HO2S signal voltage.

The HO2S contains a heater that is necessary in order to quickly warm sensor to operating temperature. The heater also maintains the operating temperature during extended idle conditions. HO2S needs to be at a high temperature in order to produce a voltage. When HO2S reaches operating temperature, the control module monitors the HO2S bias, or reference, voltage. The control module also monitors HO2S signal voltage for closed-loop fuel control. During normal closed-loop control operation, control module will add fuel or enrich the mixture, when HO2S detects a lean exhaust content. The control module will subtract fuel or lean out the mixture, when HO2S detects a rich exhaust condition. This DTC monitors HO2S voltage and detects if voltage goes out of the bias range (400-475 millivolts). If PCM does not detect that voltage went out of the bias range, a DTC sets.

Code Enable Criteria

Conditions for running DTC:

DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0300, P0351, P0401, P0404, P0405, P0440, P0442, P0446, P0452, P0453, P1258, P1404 or P1441 is not set
Engine run time is more than 409 seconds.
System operating in closed-loop.
Ignition 1 signal is 9-18 volts.
Intrusive tests are not in progress.
Scan tool output controls are not active.

Conditions for setting DTC:

HO2S voltage is steady between 400-475 millivolts for 150 seconds.
Throttle position changes more than 5 percent within one second for 6 times.

Diagnostic Procedures

Perform powertrain diagnostic system check.
- NOTE: Allow engine to cool for one-half hour before proceeding with this test. This allows HO2S signal voltage to return to bias voltage (about 447 millivolts).
Turn ignition on, with engine off. Immediately observe HO2S voltage for 2 minutes on scan tool. If HO2S voltage goes from bias voltage to greater than 350 millivolts or to less than 550 millivolts, go to next step. If HO2S voltage does not go from bias voltage to greater than 350 millivolts or to less than 550 millivolts, go to step 5.
Start and allow engine to reach operating temperature. Raise and hold engine speed at 1200 RPM for 2 minutes. Observe HO2S voltage on scan tool. If HO2S voltage is varying outside of 400-475 millivolts range, go to next step. If HO2S voltage is not varying outside of 400-475 millivolts range, go to step 5.
Observe the FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start and operate vehicle within the conditions for running the DTC or as close to FREEZE FRAME/FAILURE RECORDS data. See CODE ENABLE CRITERIA. If DTC resets, go to next step. If DTC does not reset, problem is intermittent.
Turn ignition off. Disconnect affected HO2S connector. Turn ignition on, with engine off. Connect a jumper wire between a known-good ground and HO2S harness connector terminal "B" (Purple/White or Purple wire). See Fig. 6 or Fig. 7 . Connect a jumper between a known-good ground and HO2S harness connector terminal "A" (Tan/White or Tan wire). Observe HO2S voltage on scan tool. If HO2S voltage is less than 200 millivolts, go to step 9. If HO2S voltage is not less than 200 millivolts, go to next step.
Remove both jumper wires. Check voltage between a known-good ground and HO2S harness connector terminal "A" (Tan/White or Tan wire). If voltage is greater than 4.5 volts, go to next step. If voltage is not greater than 4.5 volts, go to step 8.
Turn ignition off. Disconnect PCM harness connector C1. Check for open in Purple/White or Purple wire between HO2S and PCM. Repair as necessary. After repairs, go to step 21. If circuit is okay, go to step 16.
Turn ignition off. Disconnect PCM harness connector C1. Check for open in Tan/White or Tan wire between HO2S and PCM. Repair as necessary. After repairs, go to step 21. If circuit is okay, go to step 16.
Remove jumpers wire. Check OXYGEN fuse located in underhood fuse block. If fuse is open, go to step 12. If fuse is okay, go to next step.
Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S harness connector terminal "D" (Pink wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 17.
Connect test light between HO2S harness connector terminals "(" (Black wire) and "D" (Pink wire). If test light illuminates, go to step 15. If test light does not illuminate, go to step 18.
Disconnect harness connectors from all HO2S. Check for short to ground in Pink wire from HO2S to underhood fuse block. Repair as necessary. After repairs, replace fuse, then go to step 21. If circuit is okay, go to next step.
- NOTE: Perform test on all oxygen sensors. A condition in any sensor will cause this DTC to set.
Check HO2S ignition 1 voltage circuit (Pink wire), sensor side, for short to HO2S body. If circuit is shorted, go to step 19. If circuit is okay, go to next step.
- NOTE: Perform test on all oxygen sensors. A condition in any sensor will cause this DTC to set.
Check resistance between HO2S ignition 1 voltage circuit (Brown wire) and HO2S heater ground circuit (Brown wire) on sensor side. If resistance is 2-50 ohms, go to step 19. If resistance is not 2-50 ohms, problem is intermittent.
Turn ignition off. Check for poor connections at affected HO2S harness connector. Repair as necessary. After repairs, go to step 21. If connections are okay, go to step 19.
Check for poor connections at PCM harness connector. Repair as necessary. After repairs, go to step 21. If connections are okay, go to step 20.
Turn ignition off. Repair open in Pink wire to fuse block. After repairs, go to step 21.
Turn ignition off. Repair open in Black wire to ground. After repairs, go to step 21.
Replace the affected HO2S. After replacing sensor, go to step 21.
Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start and operate vehicle within the conditions for running the DTC. See CODE ENABLE CRITERIA. If DTC runs and passes, go to next step. If DTC resets, go to step 2.
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS. If no DTCs are displayed, system is okay.