P0155 Trouble Code

ludwis · Post by **ludwis** » Wed Apr 06, 2005 5:05 pm

During my service visit for a oil & lube job I brought my usual list of issues. First, last weekend my SES light same on and threw the P0155 codej

"Upstream Heated Oxygen Sensor Heater circuit fault - Bank No. 2. "

Does anyone know what the heck that means? My truck has a really annoying quirk related to the PCV valve. When the truck is cold and and sometimes when its hot and the RPM's drop to around 480 - 500 it will make this whistling/sucking noise. It almost sounds like your blowing across a bottle of pop. Anyway, it was making this noise when the SES light popped on. The dealer ordered a replacement sensor (Part No. 12567254 W-SENSOR) to be replaced with my cv boot issue I posted earlier.

They also tracked down an issue with my rear brakes. While driving between 1 - 5 Mph I noticed a really loud metal on metal screeching noise. Apparently it was related to a rust ridge on the rear rotors. They cleaned it off and road tested it and reported it was all gone. The last time I reported the same noise they said the rotors were "glazed" and the turned them down to clean them up. I wish I knew more about this stuff to decipher this stuff on my own.

Let me know what you guys think.

n0m4d · Post by **n0m4d** » Wed Apr 06, 2005 5:55 pm

My truck is making that same damn annoying squeeking sound in the rear end!!! I took it to the shop last week for shocks, brakes, and that problem. They put the shocks in, told be the brakes had 50% left on em (at 66k?) and gave me the same line about the glazing. It was rainy that day so it wasnt as squeaky. I'm heading back there tomorrow to get them to "fix" it again. Thanks for the info.

weaselmf · Post by **weaselmf** » Wed Apr 06, 2005 7:25 pm

The SES code is the O2 sensor on the passanger side front sensor. Mine started doin the same SES code so I swapped that sensor with the Rear passenger side sensor. The SES code changed so I guess I will have to replace the sensor, $100. The whistling noise sounds like a leaking hose between your PCV and the intake manifold.

RocK · Post by **RocK** » Wed Apr 27, 2005 6:47 pm

Speakin of Idling... What does everybody's CC run around? Now last I knew idle should be 850 and 750 in gear. Mine idles around 600 constant. I know that you idle too low and you run into problems with the oil pump not pushing enough and you could run er lean in lube. I dont think that 600RPM is an uh oh but I wouldnt wanna push my luck with lower. That is unless they have a HV pump stock...yeah right. Anyway I was just wondering and like I said that was last I knew...

ludwis · Post by **ludwis** » Sat Apr 30, 2005 8:12 am

Maybe thats what the problem is. When I have it in gear, sometimes the idle drops to ~500 RPM and it starts making this sucking or "blowing across the top of a bottle" noise. The tech said it was related to the pcv valve and it was "normal". It drives me nuts though. Maybe its just a matter of increasing the idle speed?

How does one accomplish that anyway?

RocK · Post by **RocK** » Sun May 01, 2005 10:03 am

Well after quite a bit of searching on the net, the most common idle I found is 700RPM on the 02 4.3L. It should be there whether in or out of gear (the idle control motor corrects this to keep it at the right RPM) I am gonna give the dealer a call on Monday and see what they say it should be.

I also found a few people complaining about a very low idle triggerin the oil pressure light and they were runnin somewhere around 450RPM.

Havent found nuthin on that "suckin" noise...Yet. How loud is it? And have ya had the hood up to try to see where it is commin from? Set the E-brake and slap her in gear, using a hose(even a garden hose 3 or 4ft) can help generalize an area where a noise is comming from. Just put one end to your ear and point the other. They also make tools that look like steth's but the have a solid rod on one end and best look fer knocks/pings.

kwalsh · Post by **kwalsh** » Mon Dec 18, 2006 4:10 pm

My truck threw this code, P0155. The service manual is not clear what sensor I should replace. Is it really the Upstream - Bank No. 2 sensor, or could something else have caused this?

Post by **HenryJ** » Mon Dec 18, 2006 4:30 pm

GM data wrote:DTC P0155
Circuit Description

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

The HO2S contains a heater that is necessary in order to quickly warm the sensor to the operating temperature. The heater also maintains the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. When the HO2S reaches the operating temperature, the control module monitors the HO2S bias, or reference, voltage. The control module also monitors the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop fuel control operation, the control module will add fuel, or enrich the mixture, when the HO2S detects a lean exhaust content. The control module will subtract fuel, or "lean out" the mixture, when the HO2S detects a rich exhaust condition.

This diagnostic trouble code (DTC) determines if the HO2S heater circuit is functioning properly by monitoring the time required for the HO2S to reach the operating temperature. This DTC sets when the powertrain control module (PCM) fails to detect HO2S voltage transitions above and below the bias range within a specified time.
Conditions for Running the 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 are not set.
* The HO2S voltage is between 425-475 mV at engine startup.
* The intake air temperature (IAT) and the engine coolant temperature (ECT) are less than 50°C (122°F), and are within 8°C (14.5°F) of each other at engine start-up.
* The ignition 1 signal is between 9-18 volts.
* Intrusive tests are not in progress.
* The scan tool output controls are not active.
* The scan tool is disconnected.

Conditions for Setting the DTC

The HO2S voltage remains within 150 mV of the startup voltage for a predetermined amount of time, based on ECT and air flow.
Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
* Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Important

Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

* Use the Freeze Frame/Failure Records in order to help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Freeze Frame/Failure Records can help to determine how many miles have occurred since the DTC set. The Fail Counter and the Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions such as RPM, load, vehicle speed, temperature, etc., that you observed. For an intermittent condition, refer to Intermittent Conditions . These conditions include:
o The RPM
o The vehicle load
o The vehicle speed
o The temperature
* The heater diagnostic will only run on a cold start and run once per ignition cycle.
* An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and inspect the connections for breaks or for contamination. Refer to Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

2.

Allow the engine to cool before you perform this test. If the sensor is at the operating temperature, the HO2S voltage will stay high or low. If the HO2S voltage stays between 300-600 mV, the HO2S heater is inoperative.
3.

If more than one HO2S DTC is set, the HO2S fuse may be open. Test all the related circuits going to all the heated oxygen sensors for a short to ground. If you cannot locate a shorted circuit, it may be necessary to disconnect each HO2S one at a time in order to locate a shorted sensor.
4.

This step tests whether an ignition 1 positive voltage supply is available at the sensor.
5.

This step tests whether a ground is available at the sensor.
6.

This step tests whether the HO2S heater element is internally open.
7.

Inspect the ignition 1 positive voltage circuits at the underhood electrical center for poor connections.
8.

Test the ground circuits for an open if more than one heater DTC sets.

kwalsh · Post by **kwalsh** » Mon Dec 18, 2006 7:38 pm

Thanks HenryJ. I have looked at this page a few times in volume 2 of the service manuals. I will swap out the bank 2 sensor & see what happens. I find it annoying that the service manual details of a DTC for an oxygen sensor malfunction (P0153,P0154 & P0155) fail to designate in which Bank & senosr # has thrown this DTC.

Post by **HenryJ** » Mon Dec 18, 2006 7:54 pm

Have you cleared it and it returned?
With only one failure , I would give it a second chance.

Remember the OBDII system signals emission problems. It does not predict engine failures. Don't take it too seriously. Take your time to make sure there is a real problem.

kwalsh · Post by **kwalsh** » Mon Dec 18, 2006 8:21 pm

It threw the code for the 4th time this evening. I'll see if cleaning the sensor with an alcohol wipe does the trick before I put a new one in.

Post by **HenryJ** » Tue Dec 19, 2006 4:10 am

Probably time to replace it then. Cleaning a HO2S would likely be a waste of time. You can not get to the sensor and cleaning the shield is not a big help.

I have found that the O2 sensors tend to fail in a cascade. One goes , then another, and another. If the mileage is there I would suggest biting the bullet and replacing them all. That is my plan when the time comes.
Their performance declines with age/use. After 100k miles they are likely due for replacement.

kwalsh · Post by **kwalsh** » Tue Dec 19, 2006 6:15 am

ouch, a little pricey, 3@ $80 each.....there goes my Christmas present

24digger · Post by **24digger** » Wed Dec 20, 2006 3:51 am

You might find some on ebay. I just bought 2 for my 95 which is also the same one for 02 crew, for 68 dollars for 2.

F9K9 · Post by **F9K9** » Thu Oct 23, 2008 4:19 pm

Okay, this is 3 days after I returned from the Moab trip and the first time I drove the CC since. I fired it up and threw an SES light P0155. 38K on the rig now and hopefully still under warranty. The "pre cat" may void it but, I have friends. I reset it and it is currently showing no SES for now. We shall see.

F9K9 · Post by **F9K9** » Fri Nov 21, 2008 6:21 pm

Okay, I have had the code reappear for the third time after clearing it twice. My friend, who was the service manager, at the dealer where I bought my extended warranty, at is no longer there. The original dealership shouldn't charge me anything and other dealerships are $100 deductible. Problem is that I deleted my precat with outstanding results. Original dealer may claim "modifications" caused the demise of the sensor. Rock Auto's sensors are now around $85. If, all three cascade like Brule says then, I might be better off going to my friend's new workplace and pay the $100 and hope for the best. I dunno, I am going to email him and see what happens.

Capt. Morgan · Post by **Capt. Morgan** » Sun Nov 23, 2008 2:35 pm

my 03 did the same thing 110k all i did was changed the location of where i bought my gas. but i was also running lucas fuel treatment havent used it lately but havent had any codes since changing gas stations.

F9K9 · Post by **F9K9** » Sun Nov 23, 2008 3:37 pm

Capt. Morgan wrote:my 03 did the same thing 110k all i did was changed the location of where i bought my gas......................

Well, that's a thought and I may experiment with. Prior to Moab I was only using one station without problems. I used a bunch of different flavors while on the trip. My last fill up was in KY before the first SES light. I am still waiting on a reply to my email and it may help that my friend is an acquaintance of the owner of the extended warranty company. I paid approx $1K for the warranty and it has paid off for me thus far. It expires in May or 75K miles. At 38K I do not think I need to worry about mileage. I should know more this time tomorrow because his email address is through work and he'll check it in the morning.

roadrunner · Post by **roadrunner** » Sun Nov 23, 2008 3:45 pm

Have you checked to make sure you didn't do any damage to any underneath wiring crawling around on all them rocks at MOAB? I know you said you had this code before but perhaps body-flex or wire damage may have further aggravated it? Just a thought.

F9K9 · Post by **F9K9** » Sun Nov 23, 2008 3:54 pm

Well, I think I posted the original code appearing in another thread that I am sure was definitely off topic for whatever that thread was meant to be about.

Whatever that topic was, I mentioned the SES because I was busy chasing it down. This is my second SES in over four yrs. The only other one I have had is when I went to the Jet Performance 180° t-stat. That happened in the falls when the weather changed. First 2 years I changed t-stats (5 min job with a tb spacer) and I finally solved that issue when I relocated my IAT closer to the aftermarket filter.

I never had this code before Moab.

roadrunner · Post by **roadrunner** » Sun Nov 23, 2008 4:52 pm

Man I wish I could say I had so few SES problems in the time since I bought my CC! I have to admit though I do have a few more miles on mine than yours does. I was just musing that perhaps all that rock crawling might have caused or aggravated a wiring problem. Yeah, I'm guilty of that straying topic problem too.

F9K9 · Post by **F9K9** » Sun Nov 23, 2008 5:55 pm

roadrunner wrote:......I was just musing that perhaps all that rock crawling might have caused or aggravated a wiring problem......

It's not a bad thought, though. Crawling mainly tests stuff like hitch safes, $500 custom rock slidersand $12 TSC tractor lights that are used for aux back up lights.