4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

p1151 and p1131 codes

Old 02-10-2019
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Join Date: Jan 2019
Location: Fredericksburg, Virginia
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p1151 and p1131 codes

Hello Iíve got a 1998 4.0 and I was having an issue with the truck bucking in 3,4 and 5 th gear when under a load (going up hills). I had 071 codes before and replaced coil packs,wires, fuel filter, spark plugs and check the pressure on the rail. Fuel pressure was good even while driving and bucking. So I figured next step would be fuel injectors. I replaced them yesterday while doing the injectors I replaced upper intake gaskets and torqued the studs to the proper ft pounds and in proper sequence. When I first backed it out of the shop and took it for a spin it acted perfect. Set cruise control went up hills in all gears did great. After driving for awhile it began to hesitate and miss unless giving it full throttle. Itís in and out sometimes it runs perfect sometimes it will sputter and hesitate. The CEL came on and Iím now having P1151 and P1131 codes truck also smells funny after being driven. Is it possible my injector connections are loose on a couple of them? Or is it more likely I have bad oxygen sensors?
Old 02-10-2019
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Location: Vancouver, BC
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What are codes P1151 and P1131 ?

Did you look them up?

Trust me, no one has all the codes memorized, lol.
So if you looked them up then post the english translation with the codes, makes it easier all around

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2

Not sure on 071???

P1xxx means its not a generic OBD code, it is a manufacturer specific code, since its a Ford computer then its a Ford OBD code, GM, Toyota, BMW, ect.... may use P1131 differently, might be a pressure code or ???

P0171 should have been seen first, as well as P0174, they also declare lean on bank 1 and bank 2, P0xxx are generic OBD codes and apply to all models and engines the same

Simple way to eliminate an upper intake manifold vacuum leak(has to be upper intake to effect BOTH banks of an engine) is to warm up the engine fully, let it idle, and unplug the IAC Valve
IAC valve will close and idle should drop down to 500rpm or engine may even stall, either is GOOD, it means no vacuum leak, if idle stays up then you have a leak, you just haven't found it yet.

If it was an injector issue it would only effect the bank with the faulty injector.
Lean means too much oxygen in the exhaust, so exhaust manifold leak can suck in air/oxygen, but again BOTH exhaust manifolds would have to leak to effect BOTH banks of the engine
Misfires cause lean exhaust, but there would have to be misfires on both banks to get both codes

Having the two upstream O2 sensors fail at the same time would be very very long odds, so not likely to be O2 sensor issue

MAF sensor will effect both banks
An air leak between MAF sensor and throttle plate will effect both banks
Faulty PCV Valve will effect both banks
Fuel pressure will effect both banks

Clogged exhaust will effect both banks, assuming no dual exhaust

Yes, faulty computer(PCM) can effect both banks
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