Pulling a P0118 ECT code, what does this mean?

Discussion in 'SN95 4.6L Mustang Tech' started by IronD01GTvert, Aug 28, 2010.


  1. IronD01GTvert

    IronD01GTvert Founding Member

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    So my SES Light came on and I'm showing a few codes. My scanner showed these 3: P0118, P1131 and P0172 P. I know the last 2 have to do with one of my cats, since it is effed. After looking up the codes online the P1131 says-P1131 - Lack of HO2S-11 Switch, Sensor Indicates Lean A HEGO sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time. The P0172 says-System too rich (bank1). I have a feeling If I get the cat replaced these will go away but what is the P0118? I know it has to do with "P0118 - ENGINE COOLANT TEMPERATURE CIRCUIT HIGH INPUT" but what does that mean? I also can't locate the sensor. Everyone seems to say its to the left of the alternator outside the engine block but that's a little vague. Could all 3 of these codes be related? I'm more concerned with the ECT code because I have no idea what it is. All my seaches on google and the stangnet forums haven't helped me. Any help you guys could offer would be greatly appreciated.
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  2. wmburns

    wmburns SN Certified Technician

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    P0118 -ECT Circuit High Input

    Since you asked specifically about the P0118 DTC, let's start there. The DTC indicates that the sensor's voltage return to the PCM is TOO HIGH.

    This usual is cause the a hard FAULT in the circuit. Suggest start by inspecting the wiring harnes to/from the coolant sensor. Look for loose/chaffed/burnt wires. Look at the connector itself. Is it plugged in all the way?

    It is also possible that the sensor itself is bad. Also note that the DTC refers to the cylinder head sensor but the Mustang does not have a CHT. On applications that do not have a CHT, the DTC means coolant sensor.

    OBTW, on the 4.6 SOHC the coolant sensor is located on the right hand side of the intake manifold crossover near the alternator.

    Does your scanner also monitor ODB2 data? If so, use it to monitor the engine coolant temperature. Is it reasonable?

    The PCM uses the engine coolant sensor to make various decisions regarding engine management. Things like O2 open/closed loop, engine fan settings and others depend on an accurate coolant temperature. So it may or may not be causing your other problems. IMO, it can't be helping the situation.

    However, if you have been disconnecting the coolant sensor doing other work, this could account for the DTC.

    Regarding the other DTC codes. Where do you stand regarding vacuum leaks and exhaust leaks?

    Also check your fuses. Esp fuse F2.8 in the CJB.

    >>From Ford service CD
    P0118 - Engine Coolant Temperature (ECT) Circuit High Input

    Indicates the sensor signal is greater than Self-Test maximum. The ECT sensor maximum is 4.6 volts or -50°C (-58°F). Note on some vehicles that are not equipped with an ECT sensor, CHT can be used and can set this DTC.

    Open circuit in harness
    Sensor signal short to power
    Damaged PCM
    Improper harness connection
    Damaged sensor

    ECT V PID reading greater than 4.6 volts with key ON and engine OFF or during any engine operating mode indicates a hard fault.
    #2
  3. trinity_gt

    trinity_gt Advanced Member

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    This is probably incorrect.

    P1131 points to bank 1, sensor 1 not switching and showing lean. Since this is before the cats, it's not related to them. The sensor is likely bad or the wiring is suspect.

    P0172, interestingly, contradicts P1131 by indicating a rich condition for that bank. Both codes are related to the front (pre-cat) O2 sensor or its wiring.

    You would be seeing catalyst efficiency codes, not fuel mix/sensor codes. The problem is not the cats.

    It likely means either the engine coolant temp sensor is unplugged, defective (open circuit) or the wiring to it is bad.

    It's located in the intake manifold at the coolant crossover near the front, passenger side I believe.
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  4. IronD01GTvert

    IronD01GTvert Founding Member

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    Thanks fr all the help guys. I checked the sensor and all the wires are in good shape and the sensor is plugged in and screwed in all the way. Leads me to believe that the sensor has just gone bad. ill try replacing it and see what happens.

    As far as the other codes go. Which sides of the car do these numbers refer to? I believe I have heard that bank 1 refers to whichever side cylinder #1 is located on and i believe that is the passenger side on the 01 GT 4.6L. If so Im thinking that replacing that O2 sensor should correct the problem?

    Recently I have had a slew of problems with my baby. Im sure creeping over 90k miles has something to do with it, but i just want to get her running good again. Its nice to be back to Stangnet, I hadn't logged on since 2006!! Everyone here has always been so helpful and I really appreciate it.

    (Now to change that horrific signature I have ugh!)
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  5. trinity_gt

    trinity_gt Advanced Member

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    This is correct. B1 is the passenger side.
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