CEL P0036 and P0420?

2018 FORD E-SERIES VAN
75,000 MILES • 6.8L • AUTOMATIC
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CMDGOPPS
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2018 E450 V10 (Gas) Motorhome . CEL on, P0036, P0420 showing bad O2 heater bank 1 sensor 2. replaced sensor with after market (oem plug style), cleared code, CEL returns same codes. checked INPUT line voltages (blue/ylw-12VDC, wht/org-6VDC, gray-2.5VDC, org-4.5VDC.) NO ground circuit. tested KO,EO.

Wiring issue? need OEM O2 sensor? or bad cat?
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Jul 7, 2026 at 5:10 PM
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STRAILER
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Hello,

The P0036 code is for the Bank 1 Sensor 2 oxygen-sensor heater control circuit, while P0420 indicates the Bank 1 catalytic converter is not operating efficiently, so it can be the sensor issue which is giving you both codes. Does the wiring on the old oxygen sensor match the new one? Sometimes on after market sensors they get the wiring mixed up so I would double check that. The ground for the heater is provided from the PCM which is the ORG/white wire. Here is the wiring diagram and the connector view so you can check it out. Check out the images (below). Let me know how it goes
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Jul 7, 2026 at 6:37 PM
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CMDGOPPS
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So, only 1 of those wire colors match my vehicle side pigtail IF this schematic is specifically for the 2018 e450 and I can only imagine what colors Ford used but, using just the pin out numbers, does your reference manual show or mention what voltage range I should see at the vehicle side pigtail pin out?

Thanks for the reply!
Jul 7, 2026 at 7:12 PM
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STRAILER
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Here is the connector view for a 2018 f450 v10. Let me know.
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Jul 7, 2026 at 9:29 PM
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CMDGOPPS
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cool, thanks! I have ran another live stream diag and found the input volts at normal range (.795 VDC) but have no output from short term fuel trim (N/A). I believe the owner installed a regular O2 sensor, NOT a post cat "collection sensor" as Ford calls it in their parts world. they are wired different pin outs. I will replace O2 with OEM wired sensor and rediag. Thanks for all the assist!
Jul 7, 2026 at 10:48 PM
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STRAILER
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Yep. it looks like you found it! Nice work.
Jul 8, 2026 at 1:06 AM
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