P0128 randomly came up

[x_orange90_x]

2017 Dodge Journey GT AWD 3.6L 110k Miles

 

A couple days ago I was on my way home from my in law's house and while driving the Engine light came on. I was right about in the middle of my 25 minute drive, engine warmed up and running fine. I pulled the code when I got home. It was pending and so I left it to see if it would go back off but it has not. The temperature gauge is going to the normal range, the heat appears to work fine, and nothing else seems obviously wrong. I've been reading that there are several things that CAN cause this code, not most of the time it's the thermostat. I don't want to take guesses at it and start replacing random parts, so I figured the experts here could give me an idea based on their experiences. It was in the 40s I think at the time it came on, and being October here in Michigan it's getting colder now. I can't stand NOT having remote start 🥶

[larryl]

 

Sometimes the thermostat opens and the car doesn't warm up to proper temp.

Mine has done it a few times but I just clear the code I don't mind it running a little cool and the remote start will work

Edited October 15, 2024 by larryl

[x_orange90_x]

1 hour ago, larryl said:

 

Sometimes the thermostat opens and the car doesn't warm up to proper temp.

Mine has done it a few times but I just clear the code I don't mind it running a little cool and the remote start will work

I was thinking it might be a fluke. The coolant is at the bottom of the COLD range, so it is a little low but probably not enough to trip the sensor. Also, the fan DOES switch on and off with MAX A/C on, so that's working properly. I watched it warm up leaving work today and within 3 minutes it was at 110 and after about 15 minutes of driving it was around 210-215.

 

I think I may just clear the code and see if it comes back.

[Dean H]

 

P0128 Thermostat rationality.

 

Theory of Operation- 

 

The Thermostat is considered malfunctioning if the coolant temperature does not reach the highest temperature required to enable other diagnostics, or the coolant temperature does not reach a warmed up temperature within 20°F of the Thermostat regulating temperature. The Powertrain Control Module (PCM) creates a model of the engine coolant temperature warm up cycle, based on the engine coolant temperature at start up, ambient temperature, vehicle speed and engine speed. The modeled engine coolant temperature is compared to the Engine Coolant Temperature Sensor reading. If the engine actual temperature reaches the calibrated temperature threshold before the model, the diagnostic passes and completes.

 

If the model reaches the calibrated temperature threshold before the engine actual temperature, a pass/fail determination is made based on the difference between the model and actual values. The diagnostic is considered passing if the difference between the engine actual temperature and model is acceptable when the model is greater than the engine but represents the slowest possible warm-up for a "good" thermostat.

 

When Monitored and Set Conditions

 

When Monitored: This diagnostic runs when the following conditions are met

 

With the engine running.

 

Start up coolant temperature less than 65 deg * C (149 deg * F)

 

Ambient temperature between - B deg * C (17.6 deg * F) and 50 deg * C (122 deg * F)

 

Average vehicle speed greater than (10 coolant temperature reaches 85 deg * C

 

Engine speed does not go above 5400 rpm for more than 32 seconds

 

The pass/fail determination point is reached when the coolant temp model reaches 88 deg * C 190 4°F)

 

Set Conditions:

 

The predicted coolant temperature reaches the target threshold before the actual coolant temperature and the PCM detects that the actual engine coolant temperature is too far below the what is acceptable for a good thermostat

 

Default Actions:

 

MIL. light will illuminate

 

Possible Causes

 

--- LOW COOLANT LEVEL

 

--- COOLING SYSTEM ISSUES

 

--- THERMOSTAT OPERATION

[Dean H]

Remote Start Operating Conditions.

 

In order to operate remote start, the following conditions must be met-

 

Key fob sequence must be operated within a 100 meter range of the vehicle.

 

The vehicle must be in Park

 

Fobik is not in the vehicle

 

The hazard switch off

 

Vehicle Theft Alarm or Panic is not alarming

 

Doors and hood must be closed.

 

The battery voltage is normal (11 to 15 volts).

 

--Remote Start Shut Down/Deactivate Conditions---

 

Engine will NOT start or will shut down/deactivate during any of the following conditions below.

 

Doors or hood are opened before remote unlock

 

Hazard Switch depressed

 

Panic or theft alam active

 

Brake applied. If the vehicle is remote started and the customer then unlocks and enters the vehicle, the brake application will not stall the vehicle If the vehicle is remote started and no entry is detected, brake application will shut down the engine

 

Low fuel levels, Fuel indicator active

 

A prior remote start cranked the engine, but failed to start the engine.

 

Battery voltage NOT in the normal range.

 

High (run away) or Low Idle (stall) RPM.

 

MIL Active.

 

High Engine Coolant Temperature.

 

Low Engine Oil Pressure.

Edited October 18, 2024 by Dean H

[x_orange90_x]

Okay I'm back! So since creating this thread I have had the code come back several times, probably once or twice a week. I just reset it and go for another few days. Well yesterday morning I was smelling coolant and so I checked it when I got home. Sure enough I'm losing some. The reservoir is not empty yet, but it's down near the bottom. I noticed a small puddle as I was leaving this morning. It looked to be centered under the front of the engine. I definitely need to investigate it further but we're currently under a Cold Weather Advisory with wind chills in the -20s, so I am not getting under there for a few days! 

 

What are the common areas that slow leaks spring up? Btw, I'm at 117k miles now. I read on another thread about the oil filler cap assembly and how disturbing it too much can cause a coolant leak...? Well I did just have the oil changed in November.

[2late4u]

water pump weep hole is one slow place,and the  coolant jug and hoses for another, have you replaced the thermostat since having your problem? it is so easy to do and fairly cheap as well just replace with the right coolant,not so cheap but important,,,on your leak you need to see which side of the eng it is dripping from, if the oil cooler is leaking it will probably be dripping from the drivers side towards back side of the eng,,, also if the water pump it would be the passenger side of the eng,,,also SO easy to see if the oil cooler is leaking water or oil just remove the cover off the top of the engine and use a strong led light and look straight down alongside of your oil filter housing it should be clean and dry at the bottom of you see anything you might have a leak there

[John/Horace]

Start driving with a jug of coolant in vehicle so you don’t get stuck in the cold. Keep the reservoir at half if possible until you get leak fixed. 
 

You might have more than one problem going on at once. The leak is the main priority, clearing code permanently is second. If water pump weap hole is dripping (bad main shaft bearing seal) it will drip right at the front of the engine, so drivers side coming down. Milage is a little low for that, but it’s possible. 

 

If you have rear heat there is a plastic tee fitting in the large 1.5” hose that will feed rear heater core. Leak would be high up at front of engine, right around the middle. If fitting snaps you won’t be able to drive anyway, system will empty in mins at most.

 

Most likely leak is the oil cooler heat exchanger assembly. Mine failed at 100k miles, bottom oil seals let go. It’s mounted between the vee  of the cylinder heads, on the top of engine. Usually they gush oil but glycol is also possible as it heats/cools the engine oil flowing through it. Plastic get brittle and/or o ring seals let go under pressure. Most people switch to an all aluminum style unit, they don’t seem to fail a second time. The units with black are the plastic units. Engine oil filter is part of the assembly. It’s located under the plastic intake manifold, so hard to see. The two screw in sensors are oil temperature and pressure. 
 

 

 

 

 

 

 

 

 

https://www.rockauto.com/en/catalog/dodge,2017,journey,3.6l+v6,3434428,engine,oil+filter+housing,12429

Edited 20 hours ago by John/Horace

[x_orange90_x]

10 hours ago, John/Horace said:

If you have rear heat there is a plastic tee fitting in the large 1.5” hose that will feed rear heater core. Leak would be high up at front of engine, right around the middle. If fitting snaps you won’t be able to drive anyway, system will empty in mins at most.

 

Hmm. I DO have the rear heat.. But I noticed about a week or two ago that it's not actually working 🤔 no matter what I set it to (manual, auto, High heat, etc) it still puts it cold air