7.3 eot sensor symptoms - Perfecting Your Powerstroke's oil temp

Your Powerstroke 7.3 EOT sensor (Engine Oil Temp Sensor) is a thermistor type sensor.

Meaning that it's resistance changes depending on the oil temperature.

And that techno-babble means that the EOT sensor's signal is used to determine when and how much fuel is required for optimum starting and engine operation.

7.3 EOT Sensor - Powerstroke Engine Oil Temp Symptoms

7.3 EOT Sensor Location

The 7.3's oil temp sensor is screwed into the back of the HPOP reservoir on the driver's side, just above the IPR. The 1996 - 2003 7.3 Powerstrokes have a 2-wire rectangular connector. Pre 1996 7.3 Powerstrokes have a 2-wire ROUND connector.

7.3 Powerstroke Oil Temp Sensor (EOT) Location

7.3 EOT Sensor Function / Purpose

How much fuel to deliver and when to deliver it is controlled throughout your Powerstroke's normal operating temperature range.

The EOT sensor's resistance changes depending on the temp. The EOT sensor produces a 0 to 5 volt signal that calculates temperature.

The powertrain control module (PCM) uses the value supplied by the EOT sensor control:

  1. Glow plug on time
  2. Dash glow plug lamp ON time
  3. Exhaust pressure regulator (EPR) actuation
  4. Idle speed, fuel delivery and injection timing

The PCM adjusts those as temperature (voltage) readings from the EOT sensor increase.

7.3 Oil Temp Sensor Symptoms

The EOT sensor is what I'd consider a maintenance part. Meaning it's not going to last forever.

Severe problems in the EOT circuit can be caused by a faulty or failed completely engine oil temperature sensor or wiring.

Here are some symptoms that the EOT sensor on your 7.3 Powerstroke is failing or bad:

  • Your engine starts but throws an intermittent CEL and ODB-II code
  • Your 7.3 runs rough until it warms up, then, once it's warm, it runs much smoother
  • Intermittent rough idle when cold
  • Miss/hesitation at light pedal low rpm
  • Holding medium (1000-1500) rpm in neutral causes surging and cutouts
  • Your truck may not not re-crank if the engine's hot. You have to wait 20-30 minutes for the engine to cool before it will restart.

What causes a 7.3 EOT Sensor failure?

One common problem is with the EOT sensor wiring or wiring connector. A short to ground (frayed wires) or loose wires at the connector in the EOT circuit will cause an intermittent CEL to show up. It'll also cause poor starting and running behavior.

Another problem is that your PCM could be faulty and unable to correctly communicate with the EOT sensor.

Or your 7.3 EOT sensor can simply go bad over time. And if your EOT sensor's malfunctioning or failed, you may not know about that until it's too late.

Because high engine oil temperature can be lethal to many of your 7.3 engine's major components. And though high heat can be caused by numerous things, it's the job of the EOT sensor and the engine coolant temp sensor to detect these conditions and let you know about it before things get to that critical stage.

And with an overheating oil or coolant system, things can go from bad to worse very quickly. Especially if you ignore that annoying intermittent check engine light on your dash.

7.3 EOT Sensor - Idle Speed Control

Generally, when your Powerstroke oil temperature's below 158°F, the EOT's signal tells the PCM to incrementally increase your truck's idle up to a max of 950 rpm.

Idle Speed (Vehicles with Automatic Transmission)

At oil temperatures below 32°F, low idle is incrementally increased to a maximum of 1200 RPM at - 20°F.

Idle Speed (Vehicles with Manual Transmission)

At oil temperatures below 95°F, low idle is incrementally increased to a maximum of 1200 RPM at - 20°F

7.3 EOT Sensor - PCM Default Mode

If the PCM detects an EOT sensor signal that's out of range (high or low), it will ignore the EOT sensor signal.

The PCM then defaults to assuming the engine oil temperature is -29°F for starting and 212°F for normal running.

A diagnostic scan tool will display a fixed PID value of 212°F  when the EOT sensor's in this default mode.

The CHECK ENGINE light comes on for as long as that condition exists.

Don't run your truck with your EOT sensor unplugged

Some Ford truck forum goers advocate simply unplugging the EOT sensor if it has problems, effectively telling the PCM to go into this default mode.

But the EOT system's main function is to detect other problems with the vehicle. If the EOT system circuits have problems or are disconnected they're unable to monitor the oil temperature.

So, left unrepaired or disconnected, the EOT can't detect overheating in the engine's oil delivery system and severe engine damage can occur.

7.3 Engine Oil Temp Sensor Part Numbers

After an exhaustive search I've found that there are 3 distinctly different-looking parts that are represented to be 7.3 EOT sensors. All of them also cross reference to 7.3 ECT (Engine Coolant Temperature) sensors.

7.3 EOT sensor (Old - ROUND connector)

Pre 1996 - 7.3 EOT sensor part number: WT5058 ON eBAY (ROUND Connector) - Cross references to SU201, 36407, WT5058, 5S1140, 9362, 4H2

7.3 Oil Temp Sensor with Round Connector
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Retrofitting 1994-1995 EOT to the new style sensor

1994 and 1995 old style round connector 7.3 EOT sensors can be switched to the new style (Rectangular) ones below. (REQUIRES Pigtail Replacement: SEE "Wiring Harness" section BELOW)

7.3 EOT sensor (NEW - Rectangular Style Connectors)

7.3 Oil Temp Sensor with Rectangular Connector

1994-2003 - Superseded replacement 7.3 EOT Part Number - F5AZ12A648A or F5AZ12A648AB (Which most often comes up described as the 7.3 Engine Coolant Temp Sensor, but is used interchangeably as a 7.3 EOT sensor)

However, a quick check on fordparts.com and their system converts that part number to...

1994-2003 - Ford OEM superseded replacement 7.3 EOT Part Number - 3F1Z12A648A (Ford calls it a "SENDER ASY")

And finally...

1994-2003 - Alliant Power has a superseded replacement 7.3 EOT Sensor — Part number: AP63436. It replacesF5AZ12A648AB, 3F1Z12A648A, DY961, DY1144 as a direct replacement for them all.

After more research than I like to... Okay, that's not true — I love researching this stuff.

Anyway, the two new parts are represented as being interchangeable. In fact, there are several forum threads where DIY 7.3 owners swap the ECT and EOT sensors back and forth, attempting to troubleshoot a 7.3 EOT problem.

7.3 EOT Sensor - AP63436, 3F1Z12A648A

7.3 EOT Sensor - ECT (Coolant Temp Sensor)
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7.3 EOT/ECT Sensor - F5AZ12A648AB

My suggestion — remove your 7.3 engine oil temp sensor, see which one it is, and replace it with the same one. If you're not that motivated or you want to upgrade to one of the new sensors, it shouldn't matter which one you use.

But for pete's sake, don't just unplug it...

NOTE: These sensors fit 1994 - 2003, 7.3 Powerstroke engines. HOWEVER, after 1995 Ford changed the round wiring connector to a two wire rounded rectangular conector. So early model (1994 and 1995) OBS 7.3 Powerstrokes will need to rewire the wiring harness (pigtail) connector with the new style.

Check to see which wiring connector you have.

Replacing an old style (round) 7.3 EOT sensor

If you don't want to replace your old style (1994-1995 ROUND) wiring harness and connector, but you need to replace your sensor, use part # WT5058 ON eBAY:

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7.3 EOT Sensor Wiring Harness - Replacing the Pigtail

If your EOT sensor pigtail is shorted, frayed or the connector is damaged, you'll need a new 7.3 EOT sensor wiring harness (pigtail).

Also, if you have a 1994 - 1995 OBS 7.3 Powerstroke, your connection is most likely the old round connector. So when you replace your EOT sensor to a new style, you'll need this pigtail to retrofit to the new 2-wire rounded rectangular connector.

7.3 EOT Sensor Wiring Harness (Pigtail)
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Ford part number: 3U2Z-14S411-HYB eBAY LINK (A search for this part number will turn up 7.3 engine coolant temp sensor harness, but the parts are interchangeable)

7.3 EOT Sensor - Common Resistance Values

  • 0.53v at 248°F and 1.19 K ohms
  • 0.96v at 205°F and 2 K ohms
  • 1.37v at 176°F and 3.84 K ohms
  • 4.37 vat 32°F and 7.21 K ohms
  • 4.60v at -5°F and 8.22 K ohms

With those, the engine oil temp sensor and PCM ensure that enough torque and power is available no matter the temperature.

7.3 Oil Temp Sensor - Diagnostic Trouble Codes

  • 0197 = Signal was less than .04 volts for more than 0.2 seconds
  • 0198 = Signal voltage was greater than 4.9 volts for more than 0.2 seconds.
  • 0195 = Engine oil temperature less than 158° F during KOER (Key On Engine Running) test (Access denied.) or engine oil temperature greater than 242° F during KOER test (Aborts Test.)

7.3 EOT Sensor - Tool Size and Torque Values

7.3 EOT Sensor Torque Value

I found no documentation for the 7.3 on EOT torque value. If you know where I can find it, shoot me a quick note from our CONTACT PAGE.

** DISCLAIMER: after hours of researching, trying to find the correct torque value for the 7.3 EOT sensor, the closest I came was the values for the 6.4L Powerstroke EOT sensor: 159 INCH lbs. or 18 Nm. Use that value at your own risk.

7.3 EOT Sensor Socket Size

And finally, depending on the version of the EOT sensor that you have in your truck or purchase as a replacement, you can use a 21mm, 22mm, or 1" deep well socket.

If you're worried about damaging the plastic connector around the top of the sensor or it looks like a deep well won't have the clearance, use a 21mm or 22mm open-ended wrench instead.

Leave a Comment:

Rissling says

I just found this 7.3 Powerstroke website….awesome! Easy read to find answers to 7.3 problems and great links to parts and tech. data. Keep it up!

Reply
    Steve says

    Thanks! I’m just fixing my own 7.3 Powerstroke Diesel and trying to capture as much of the tools, tips, and tricks that I can.

    Reply
Dennis Coberly says

Have just replaced eot sensor on my 2002 7.3 along with ect sensor, water pump, engine oil cooler, and radiator. Truck will not start on initial try and I don’t want to make things worse if I did something wrong. From this post it would seem that the loss of oil when removing the old sensor might cause a problem with initial startup. Is this a common problem or even a possibility? Any help would be greatly appreciated.

Reply
    Steve says

    Dennis,

    “Have just replaced eot sensor on my 2002 7.3 along with ect sensor, water pump, engine oil cooler, and radiator…”

    Might need a little more info:
    Does your 7.3 crank at all?
    Does it turn over but runs rough initially?
    Etc…

    And do you have any CEL codes on your truck?

    That’s a lot of 7.3 Powerstroke parts to upgrade at the same time. Chances are one of them is malfunctioning or doesn’t have full fluid. Top off your HPOP reservoir to make sure your HPOP has enough oil to pressurize the fuel delivery system.

    Also, if your truck cranks but won’t start and it started before the upgrades, recheck the installation of each part, including making sure that your coolant fluids are up to levels and also check the wiring harness of your EOT sensor. Try cranking it over with the EOT sensor unplugged to see if the new EOT or wiring harness is causing poblems

    Reply
Steven says

Thank you for this site I had a death valley oil leak and dumped 15 quarts of oil in a customer’s driveway yesterday 7/3/18. I freaked out when I pulled my dip stick and it was on add mark. I add 2 gallons of oil and drove home checking it every few miles by I made home. After I gunked it down with degreaser and found it was the o ring on the hpop line fitting. I pulled line and plug and replaced o ring. Saved me a lot of time and money thanks yall👍👏

Reply
    Steve says

    Glad you limped your 7.3 Powerstroke home safely! Yep the 7.3 HPOP is under so much pressure it can pump out a lot of oil in a hurry!

    Reply
Timothy Bamford says

This is the most valuable site I have ever found on the internet, thank you so much for such a valuable tool. I have a 2003 Excursion 7.3 I bought new and need to do as much maintenance as I can due to a very limited income.

Reply
    Steve says

    Thank you. I’ve put a lot fo research and effort into it. Glad to help!

    Steve

    Reply
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