2.3L & 2.5L I4 Tech General discussion of 2.3L and 2.5L I4 Ford Ranger engines.

CEL Codes

  #1  
Old 03-10-2019
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CEL Codes

i have a 1997 Ranger 2.3 2wd i have 5 codes and ive been looking them up but cant get the same answer everywhere i look
P0705 Trans Range Malfunction
P1401 dpfe High Which i changed one off a no CEL truck and got the low code so not sure
P1131 Front Bank 02
P0171 System Lean Bank 1
P0001 Fuel Pressure Regulator

Just want to make sure these are the right descriptions of the codes
 
  #2  
Old 03-10-2019
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These are unusual codes, how long have to had this ranger and have there been any running issues?

P0705 Transmission Range Sensor Circuit malfunction
Applies to automatic transmission vehicles only
On the drivers side of transmission you will see a black plastic piece on the shift rod with wires plugged in, this is the DRT(digital transmission Ranger) sensor, it tells the computer(PCM) what "gear" driver has selected
It is a Ground sensor, and when key is on it sends that ground to PCM via the DTRs position, so PCM should always get a Ground on one of its wires 4 wires if not it will set P0705
Best thing would be to visually inspect this sensor, it can be hit by road debris, it can be removed and tested

P1401 Diff Pressure Feedback EGR Circuit High Input
Codes that start with P0 are generic OBD2 codes that apply to all vehicles, regardless of maker
P1 means is a manufacturer specific code, in this case a Ford code, just FYI

DPFE sensor has 2 hoses that run to the EGR tube, one closer to the EGR valve one farther away
The DPFE sensor tells PCM the pressure difference between the 2 hoses
When EGR valve is closed the hoses have the same pressure, no difference
As EGR valve is opened, by the PCM, the closer hose will have less pressure, this is how the PCM can tell EGR valve is working, and also how much exhaust is flowing into the intake

All exhaust has water vapor in it, this is why tail pipes drip water and why exhaust systems rust from the inside out
So the DPFE sensor and its hoses can get water vapor inside, and this is what usually causes DPFE sensors to fail
But you also need to clean out the hoses they can get plugged up with water vapor and carbon
High or low circuit can mean one of the hoses is plugged up or cracked/broken

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P0171 System too Lean (Bank 1)
Similar codes
Bank 1 is passenger side of V6 or V8 engine, Bank 2 is Drivers side
Since you have a 4cyl in line engine it just has Bank 1

An O2 sensor generates its own voltage, they do have a heater built in and that is powered by the vehicle, but these codes apply to the sensor part not the heater part, which are different codes
So they have 4 wires, 2 for the heater and 2 for the sensor
O2 sensors need to be above 600degF to operate, which is why they are heated, but it still takes a few minutes after cold start to warm them up

O2 sensor voltage is low and a narrow range, .1v to .9v less that 1volt
.1v is Lean
.9v is Rich

An O2 sensors voltage should change(switch) rapidly once its warmed up, switching from .2 to .6 volts a few times a SECOND, think Sine Wave with .4v as center, computer changes open time for fuel injectors constantly to keep O2 voltage centered/averaging .4v

P0171 means computer is having to open fuel injectors longer than it calculated to keep O2 sensor at .4v
P1131 means it doesn't seem to be switching(changing voltage) fast enough for the Ford computers liking and is lower than it likes, lean

Lean codes are often associated with vacuum leaks since unreported air is being sucked into the engine, this "extra air" throws off the computer's calculations of the amount of fuel to add.
If a DPFE hose was leaking, broken, that could allow extra air to be sucked into exhaust system, causing lean code and DPFE code as well

Lower than normal fuel pressure can also cause Lean codes because not as much fuel is flowing in from an injector when it opens
1997 and older Rangers should have 30-40psi fuel pressure

The P0001 code is the real oddball, it means fuel pressure regulator(FPR) sensor circuit is out of range
1997 Ranger doesn't have an FPR sensor
It has a mechanical FPR on the engine, valve with a spring, no wiring at all

1998 and up Rangers used a newer fuel system, Returnless system that runs 55psi fuel pressure, and did it use an FPR sensor on the top of the gas tank
 

Last edited by RonD; 03-10-2019 at 03:27 PM.
  #3  
Old 03-10-2019
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Rond thanks for the accurate descriptions of the codes and i have been driving the truck for maybe 6 months actually runs pretty good didn't know i had any codes until i changed my cluster bulbs to leds. The P0001 code only showed up on 1 scantool out of 3 i assume it was a fluke then since it doesnt fit my year
 
  #4  
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Forgot to add
Actual Lean running will cause pinging/knocking when accelerating
Also limited EGR flow will as well

So the Check Engine(CEL) bulb was burned out?

Or were these just history codes so you don't know when they were set?
 
  #5  
Old 03-10-2019
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yeah the bulb was burned out so im not sure how long they gave been thrown but truck definitely doesn't ping or knock
 
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