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O2 Sensor Voltage #4111047 05/31/16 01:36 AM
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Falcon_LS Offline OP
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Long story short, my Grand Marquis was built to run leaded gas and as such, had no oxygen sensors or catalytic converters from the factory. The wiring and connectors for the oxygen sensors are there, and I've just installed a set of upstream sensors, so I could provide the tuner with STFT/LTFT data.

Problem I have now is, there's no voltage going to the sensors. Initially I had no fuel trim data, so I checked voltage, which was zero. The sensors are enabled in the PCM. Any ideas?


Petro-Canada Duron HP 15W-40 CK-4/SN
99 Explorer: H17W02
00 Pajero: XG9688
01 Grand Marquis: XG2
05 Envoy: XG9837

Motorcraft 5W-50:
18 Mustang GT: XG10575
Re: O2 Sensor Voltage [Re: Falcon_LS] #4111096 05/31/16 06:00 AM
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Miller88 Offline
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Does the PCM have drivers for the oxygen sensors?

Without sensors ... does it just run pig rich all the time?


18 Forester 2.5I 6M
00 Jeep XJ
01 F-350 4x4 5M
Re: O2 Sensor Voltage [Re: Falcon_LS] #4111099 05/31/16 06:17 AM
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Falcon_LS Offline OP
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By default, the engine ran in open loop mode, as there were no oxygen sensors - so no real issues running rich. Once the modified engine went in, the PCM's cranking file was programmed to accommodate upstream oxygen sensors. You got the usual lopey idle associated with bigger cams, but that's about it. There's no real issue driving it either, other than the 4,000 rpm rev limiter until the tuning process is completed. It does, however, idle rough.

The wiring harness for the sensors are there, along with the connectors, but for some reason or another, there's no voltage going to them. The tuner said to check the fuse, which this particular application does not have, and to check for voltage to the O2's.


Petro-Canada Duron HP 15W-40 CK-4/SN
99 Explorer: H17W02
00 Pajero: XG9688
01 Grand Marquis: XG2
05 Envoy: XG9837

Motorcraft 5W-50:
18 Mustang GT: XG10575
Re: O2 Sensor Voltage [Re: Falcon_LS] #4111105 05/31/16 06:25 AM
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Trav Offline
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Look at O2 12v circuit in the wiring diagram.
It looks like there is a battery junction box with a couple of 15A fuses in it.


Last edited by Trav; 05/31/16 06:38 AM.

ASE L1, Master. Deutsch Meisterbrief.
Re: O2 Sensor Voltage [Re: Falcon_LS] #4111134 05/31/16 07:12 AM
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The O2 sensors don't require any voltage feed to operate. The voltage feed you see is for the O2 sensors built in heaters. The heaters bring the O2 sensors up to operating temperature more quickly.

Early on O2 sensors were a one wire with no heaters..the O2 sensor itself (with or without heaters) generates voltage based on the O2 and the ECU interprets the signal.

Re: O2 Sensor Voltage [Re: Trav] #4111179 05/31/16 08:04 AM
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Falcon_LS Offline OP
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Originally Posted By: Trav
Look at O2 12v circuit in the wiring diagram.
It looks like there is a battery junction box with a couple of 15A fuses in it.



Just had a look that that, then I noticed this is for an '03. There appears to be no HEGO fuse for '01/'02. frown


Petro-Canada Duron HP 15W-40 CK-4/SN
99 Explorer: H17W02
00 Pajero: XG9688
01 Grand Marquis: XG2
05 Envoy: XG9837

Motorcraft 5W-50:
18 Mustang GT: XG10575
Re: O2 Sensor Voltage [Re: DB_Cooper] #4111259 05/31/16 10:13 AM
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HerrStig Offline
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Originally Posted By: DB_Cooper
The O2 sensors don't require any voltage feed to operate. The voltage feed you see is for the O2 sensors built in heaters. The heaters bring the O2 sensors up to operating temperature more quickly.

Early on O2 sensors were a one wire with no heaters..the O2 sensor itself (with or without heaters) generates voltage based on the O2 and the ECU interprets the signal.
This^

Re: O2 Sensor Voltage [Re: DB_Cooper] #4111343 05/31/16 12:11 PM
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Trav Offline
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Originally Posted By: DB_Cooper
The O2 sensors don't require any voltage feed to operate. The voltage feed you see is for the O2 sensors built in heaters. The heaters bring the O2 sensors up to operating temperature more quickly.

Early on O2 sensors were a one wire with no heaters..the O2 sensor itself (with or without heaters) generates voltage based on the O2 and the ECU interprets the signal.


I understand that, the tuner wanted know if they were being turned on including the heaters. No power going to the heaters and no CEL would seem to mean they are not turned on in the PCM tune.
The car has no CEL and no stored coded.


ASE L1, Master. Deutsch Meisterbrief.
Re: O2 Sensor Voltage [Re: Falcon_LS] #4111975 06/01/16 01:34 AM
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Falcon_LS Offline OP
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So Trav and I have been going through this through PM.

It seemed the #6 (F2.6) fuse in the CJB is what powers the HEGO's - but that also powers the instrument cluster, LCM and buzzer diodes and those all work. Also checked 50 amp # 11 fuse in the BJB, which powers the CJB for the sake of it, and that's good too.

Interesting thing is, I programmed X-Gauges on my ScanGauge-II to view oxygen sensor data as a percentage. On the drive to work this morning, it seemed to be getting data - not sure if it's a gestimate based on throttle position or something else, of if it's actual feed from the sensors. There's nothing for STFT/LTFT though.


Petro-Canada Duron HP 15W-40 CK-4/SN
99 Explorer: H17W02
00 Pajero: XG9688
01 Grand Marquis: XG2
05 Envoy: XG9837

Motorcraft 5W-50:
18 Mustang GT: XG10575
Re: O2 Sensor Voltage [Re: Falcon_LS] #4112164 06/01/16 08:34 AM
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SHOZ Offline
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The common O2 sensors will generate a voltage signal that the ECU can read, no voltage input needed.

http://www.ngk.com.au/oxygen-sensors/technical-information/how-does-the-oxygen-sensor-work


2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual
Re: O2 Sensor Voltage [Re: SHOZ] #4112174 06/01/16 08:43 AM
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Trav Offline
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But it does need 12v for the heater. If they are not turned on in the PCM they will also not commanded to heat either.


ASE L1, Master. Deutsch Meisterbrief.
Re: O2 Sensor Voltage [Re: Trav] #4112204 06/01/16 09:12 AM
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SHOZ Offline
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Originally Posted By: Trav
But it does need 12v for the heater. If they are not turned on in the PCM they will also not commanded to heat either.
Depends if it has a heater. And if the car never had O2s then there is no need for a heater.


2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual
Re: O2 Sensor Voltage [Re: SHOZ] #4112212 06/01/16 09:18 AM
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Trav Offline
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It has the original 4 wire wire sensor harness connectors tucked up out of the way, its the same as US models only the O2 is disabled in the PCM.


ASE L1, Master. Deutsch Meisterbrief.
Re: O2 Sensor Voltage [Re: Falcon_LS] #4112215 06/01/16 09:20 AM
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SHOZ Offline
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Still if the ECU is not looking for heater current draw the heater is not needed.


2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual
Re: O2 Sensor Voltage [Re: SHOZ] #4112226 06/01/16 09:33 AM
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Trav Offline
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Talk to the tuner and work it out will him. He turned them on and wanted to know if he had the 12v at the heater wire, I just tried to show him where they were to test them.


ASE L1, Master. Deutsch Meisterbrief.
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