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insite

P1117 and P1121 on NEW O2 Sensors

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here's the story: just did a bunch of work on my car. i had a dead O2 sensor (reading open on the OBDII scanner, P0410) and some other things to do. i wound up doing a light flywheel, clutch, headers, and muffler (my car is a 2.5L, so i did not remove any cats). i also replaced BOTH O2 sensors behind the cats with new OEM style Bosch (direct plug-in).

i am now getting P1117 and P1121, indicating inadequate heating on both of the brand new sensors. what gives? does anyone know what the resistance across the heating elements is supposed to be? any ideas as to what would cause this? when i clear the codes with the scanner, they come back pretty quickly.

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I am confused P0410 is: Secondary Air Injection System - Signal Implausible (Cylinders 1 - 3). That code usually means the secondary air pump is not triggered - not O2 sensors.

P1117 and P1121

1. Remove connector of 02 sensor 1/2 after catalytic converter.

2. Connect ohmmeter on pin side to pins 1 and 2.

Display: 1.8 - 2.5 ohms at 20°C.

3. Connect ohmmeter on pin side to pin 1 and 02 sensor housing.

Display: infinite ohms

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I am confused P0410 is: Secondary Air Injection System - Signal Implausible (Cylinders 1 - 3). That code usually means the secondary air pump is not triggered - not O2 sensors.

P1117 and P1121

1. Remove connector of 02 sensor 1/2 after catalytic converter.

2. Connect ohmmeter on pin side to pins 1 and 2.

Display: 1.8 - 2.5 ohms at 20°C.

3. Connect ohmmeter on pin side to pin 1 and 02 sensor housing.

Display: infinite ohms

thanks for the reply. had a bout of dyslexic typing: P0140, not P0410. since it's highly unlikely that BOTH of these brand new O2 sensors are defective, what else could cause this? thanks.

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Ok, P0140 makes more sense.

Are the connectors/wires good?

Are the new sensors the right part?

they all look to be in good shape. i pulled up the carpet from the trunk to inspect the wiring at the back side of the plugs. they seem to be okay. the new sensors are direct fit bosch that plug into the OEM harness w/ no mods. i'll cross reference the part number on the box with the old one when i get home. i guess it's possible they're not the right sensors, but i bought them from two different places. chances of them both being wrong are slim....

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I replaced all 4 of my O2 sensors this winter and got the same codes P1117 and P1121 with P1115 and P1119 pending. They were Bosch's 13806 as well with original fitment. The CEL comes and goes. I'm thinking of putting my old ones back to see if the codes will go away and stay away.

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I replaced all 4 of my O2 sensors this winter and got the same codes P1117 and P1121 with P1115 and P1119 pending. They were Bosch's 13806 as well with original fitment. The CEL comes and goes. I'm thinking of putting my old ones back to see if the codes will go away and stay away.

wow; what pieces of crap. you figure when you use the more expensive german part, it should work better than the generic cheap part. apparently not. i guess i'll just have to figure out what resistor i need to run in parallel with the sensor to clear the code. once i figure this out, i'll post back here.

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I replaced all 4 of my O2 sensors this winter and got the same codes P1117 and P1121 with P1115 and P1119 pending. They were Bosch's 13806 as well with original fitment. The CEL comes and goes. I'm thinking of putting my old ones back to see if the codes will go away and stay away.

wow; what pieces of crap. you figure when you use the more expensive german part, it should work better than the generic cheap part. apparently not. i guess i'll just have to figure out what resistor i need to run in parallel with the sensor to clear the code. once i figure this out, i'll post back here.

Hey Insite,

Try removing them and reconnecting them 180 degrees. It might just be that the pin connections are backwards.

Hope it works!

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I replaced all 4 of my O2 sensors this winter and got the same codes P1117 and P1121 with P1115 and P1119 pending. They were Bosch's 13806 as well with original fitment. The CEL comes and goes. I'm thinking of putting my old ones back to see if the codes will go away and stay away.

wow; what pieces of crap. you figure when you use the more expensive german part, it should work better than the generic cheap part. apparently not. i guess i'll just have to figure out what resistor i need to run in parallel with the sensor to clear the code. once i figure this out, i'll post back here.

Hey Insite,

Try removing them and reconnecting them 180 degrees. It might just be that the pin connections are backwards.

Hope it works!

is that even possible?

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I replaced all 4 of my O2 sensors this winter and got the same codes P1117 and P1121 with P1115 and P1119 pending. They were Bosch's 13806 as well with original fitment. The CEL comes and goes. I'm thinking of putting my old ones back to see if the codes will go away and stay away.

wow; what pieces of crap. you figure when you use the more expensive german part, it should work better than the generic cheap part. apparently not. i guess i'll just have to figure out what resistor i need to run in parallel with the sensor to clear the code. once i figure this out, i'll post back here.

Hey Insite,

Try removing them and reconnecting them 180 degrees. It might just be that the pin connections are backwards.

Hope it works!

is that even possible?

Insite

I'll probably go through the same as I changed the location of my O2 sensors they are now 2.5 feet apart with the new headers and Hi Flow Cats.

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Insite

I'll probably go through the same as I changed the location of my O2 sensors they are now 2.5 feet apart with the new headers and Hi Flow Cats.

you'll probably have a different host of problems. where did you get your cats, BTW?

thinking more about my issue with the O2 sensor heating, i'm guessing that the ECU just monitors voltage on the heating element circuits and calculates impedance that correlates to the correct heating wattage. since the old sensors didn't throw these codes, i can only assume that bosch has either changed the heating element design OR their quality control sucks. either way, adding resistors in series to increase impedance or in parallel to decrease it should solve the problem.

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I replaced all 4 of my O2 sensors this winter and got the same codes P1117 and P1121 with P1115 and P1119 pending. They were Bosch's 13806 as well with original fitment. The CEL comes and goes. I'm thinking of putting my old ones back to see if the codes will go away and stay away.

wow; what pieces of crap. you figure when you use the more expensive german part, it should work better than the generic cheap part. apparently not. i guess i'll just have to figure out what resistor i need to run in parallel with the sensor to clear the code. once i figure this out, i'll post back here.

Hey Insite,

Try removing them and reconnecting them 180 degrees. It might just be that the pin connections are backwards.

Hope it works!

is that even possible?

Hey Insite,

From my experience it is possible to install them backwards. I did a write up on 986forum showing the subtle differences between the Walker and Bosch brand for my 2.5 Boxster (at least in my case----used Walker brand---BTW, been very happy with them) regarding the wiring and the different contact points.....

...anyway, it wouldn't hurt to try it on one of them and reset your CEL and see if the code pops up again. If it doesn't work....then, maybe mine were just an anomaly.

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I replaced all 4 of my O2 sensors this winter and got the same codes P1117 and P1121 with P1115 and P1119 pending. They were Bosch's 13806 as well with original fitment. The CEL comes and goes. I'm thinking of putting my old ones back to see if the codes will go away and stay away.

wow; what pieces of crap. you figure when you use the more expensive german part, it should work better than the generic cheap part. apparently not. i guess i'll just have to figure out what resistor i need to run in parallel with the sensor to clear the code. once i figure this out, i'll post back here.

Hey Insite,

Try removing them and reconnecting them 180 degrees. It might just be that the pin connections are backwards.

Hope it works!

is that even possible?

Hey Insite,

From my experience it is possible to install them backwards. I did a write up on 986forum showing the subtle differences between the Walker and Bosch brand for my 2.5 Boxster (at least in my case----used Walker brand---BTW, been very happy with them) regarding the wiring and the different contact points.....

...anyway, it wouldn't hurt to try it on one of them and reset your CEL and see if the code pops up again. If it doesn't work....then, maybe mine were just an anomaly.

I'm relatively new to the Boxster community but I have had a little experience regarding the O2 sensor subject. On my prior car (Mustang Cobra) I went through a couple of O2 sensor problems / replacements, it turns out the Bosch's would last 2 to 5 months. Ford OEM was the way to go, the guys from the parts shop and the forums mostly felt the same.

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Insite

I'll probably go through the same as I changed the location of my O2 sensors they are now 2.5 feet apart with the new headers and Hi Flow Cats.

you'll probably have a different host of problems. where did you get your cats, BTW?

thinking more about my issue with the O2 sensor heating, i'm guessing that the ECU just monitors voltage on the heating element circuits and calculates impedance that correlates to the correct heating wattage. since the old sensors didn't throw these codes, i can only assume that bosch has either changed the heating element design OR their quality control sucks. either way, adding resistors in series to increase impedance or in parallel to decrease it should solve the problem.

They are HiFlow stainless steel made by Megaflow.

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Hey Insite,

From my experience it is possible to install them backwards. I did a write up on 986forum showing the subtle differences between the Walker and Bosch brand for my 2.5 Boxster (at least in my case----used Walker brand---BTW, been very happy with them) regarding the wiring and the different contact points.....

...anyway, it wouldn't hurt to try it on one of them and reset your CEL and see if the code pops up again. If it doesn't work....then, maybe mine were just an anomaly.

thanks; i looked at the plug and it is a foolproof design. it's not physically possible on my car to plug the OEM style sensor in backward. additionally, i believe it would throw an P0140 code in addition to the P1117 if it were somehow installed backward.

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I went thru something similar on my 97 Saturn. Replaced front O2 sensor and the code kept coming back. Asked Saturn and they said use OEM sensor, and not Bosch. Tried Denso OEM sensor and same problem. Was going down the path towards thinking I needed a new computer. I called an automotive techline for advice and they suggested a loose wiring problem. Well after disconnecting and reconnecting to check continuity of wires, including the harness connectors at the computer, everything magically cleared up. Conclusion it was a loose connector at the computer that had worked itself loose through vibration over the years. End of story!

They also said the O2 sensors at the rear of the Cats don't do anything, either, and rarely need replacing for performance reasons. The front sensors are the ones involved in controlling the mixture. However if the rear O2S has a wiring fault it would probably set off alarms such as you MAY be geting.

/Regards/

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insite,

Sounds like bad connectors, bad sensors or wiring got knocked loose or pinched during your upgrades. Double check your leads all the way from the DME to the sensors. Compare the connector on the Bosch to the old o2 connectors. Do the leads look the same? Coded wiring? Do you get similar ohm readings across the leads?

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insite,

Sounds like bad connectors, bad sensors or wiring got knocked loose or pinched during your upgrades. Double check your leads all the way from the DME to the sensors. Compare the connector on the Bosch to the old o2 connectors. Do the leads look the same? Coded wiring? Do you get similar ohm readings across the leads?

the new sensors are good & the connectors are clean. since i replaced only the sensors after the cats, i think there's a good chance that the sensors before the cats (130k miles on them) are nowhere near as reactive & the DME is getting confused. all the porsche techs are telling me that all sorts of wierd codes can trip if you don't replace all 4 sensors at roughly the same time. they seem to think the codes will clear once in replace the primary sensors. they're on the way from pelican now. for those in the market, they have the best rate by FAR on the OEM socketed bosch sensors for the 2.5L cars: $96 each.

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****. replaced the last two O2 sensors and still throwing 1117 / 1121. will have to trick the computer into behaving.

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****. replaced the last two O2 sensors and still throwing 1117 / 1121. will have to trick the computer into behaving.

Reseat the harness connectors at the computer. Also some of the sensors in the engine bay.

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****. replaced the last two O2 sensors and still throwing 1117 / 1121. will have to trick the computer into behaving.

This is almost the same thing I'm trying to figure out. I've been getting 1117 and 1119. I got these after I replaced all my O2 sensors as well, but with generics. So 2 work fine and 2 don't. I then replaced one of the new ones and still got the same result. The funny thing is that if I drive above 3000 rpm, any pending codes clear and don't get a CEL, but I get the pending code and eventually a CEL if I drive at 2600 rpm or less. It is speed independent. I double and triple checked the wiring and connections. And I reseated the harness as well.

Edited by heyjae

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I recommend you use the factory trouble shooting flow chart for this car and these troube codes. Here is an example for a Saturn. Otherwise you are just guessing. It could bsomething besides the actual o2 sensor or wiring and these charts will tell you what other things could possibly cause this problem.
Sorry the diagrams and flow charts didn't save on that last post. But the idea is that each auto manufacturer should have a factory service manual for the electronics that will take you step by step through troubleshooting these problems and codes. It is usually a flow chart diagram.

This is where you can educate me on how to find these manuals for a porsche boxster. I would expect a dedicated manual just for the DME since it so complicated. I have seen a Bosch manual dedicated to emission control systems but don't know what cars and years it covers.

Also if the car is OBD-II compliant, that means you can plug the standard automotive computer diagnostic equipment (found at any shop or auto parts store) in and see what the computer thinks is happening when the engine is running. Most cars sold in the US starting in 1997 are OBD-II compliant. This is a law to help the emissionc ontrol inspectors as well as repair facilties. A quick check shows Porsche became compliant with OBD-II in 1997.

There are different levels f sophistication in this equipment. There are handheld code scanner that just reads and clears codes, that sells for less than $100. There is software that runs on a laptop and uses an adapter between the OBD-II port and USB port for around $200. It will read and display all that is going on in the computer and display really cool graphs and charts of all of the sensor reading including temp, O2, RPM's, throttle position, spark advance, etc. but you still need to know what you are doing to make heads or tails of these readings. There are also more sophisticated handheld units that will do many of these things.

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yeah, i guess i probably should have busted out the manuals first.....just figured someone had run into this & had the quick fix. i do have the factory shop manuals and OBD II supplements I - III. oddly, the diagnostic procedure for O2 sensors after the cats with insufficient heating codes are not in the books. there ARE, however, instructions for the sensors in FRONT of the cats. maybe there's another OBD II supplement that i don't have.

anyway, i found out something interesting: the o2 sensor heating circuits are wired in parallel through a relay controlled by the ECU. the ECU actuates the relay, which in turn activates the heating cicrcuits. since both of the sensors have insufficient heating even though they are wired in parallel, this leads me to suspect the relay itself. it does not, however, give the location of this relay. does anyone know where it is?

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does anyone know if all four O2 sensors have heating actuated by the same relay, or is it two different relays?

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