P0118 on a new built block.
 

Hello,

I have a built motor and its in the car. I was going ahead with priming the oil pump.
Disconnect crank position sensor
Pull fuel pump fuse
But everytime put the car on ACCESSORY mode the car think its overheated. I thought it would be the coolant temp sensor and i replaced that but same result. Dash coolant gauge goes past H thinking its overheated then rad fans come on.

I put the car back to stock but isnt on the stock tune right now, i was trying to put it on the stock tune before this happened.

Edit: i have tried to clear the code but rad fans comes back on and coolant temp gauge goes back to the H back to the issue.

Edit2: car back on stock tune but still car get that P0118 and rad fans come on.
My engine harness toast? Any help or suggestions appreciated.


Edit 3:

Okay so apparently the connectors for the the knock sensor and coolant temp sensors are the same. I forgot to mention P0327 was there as well. I switched the two now everything is fine.

I added in photos of the plugs. I already forgot which plug goes to which sensor based on the color of the wires. But yes, theyre the exact same plug so anyone else that has car in accessory mode that post P0327 and P0118 may have their plugs switched on the wrong sensors.

Sounds like a harness or ECM issue....check resistance and voltage.

DTC P0118 ENGINE COOLANT TEMPERATURE CIRCUIT HIGH INPUT CIRCUIT DESCRIPTION
The resistance of the thermistor built into the E.F.I. water temperature sensor changes as the engine coolant temperature changes. The E.F.I. water temperature sensor is connected to the engine control computer in the same way the inlet air temperature sensor is connected.
NOTE:
When this DTCs is stored, the engine control computer enters fail-safe mode. The engine control computer fixes the specified engine coolant temperature at 70°C {158°F} during the fail-safe mode operation. The engine control computer continues fail-safe mode operation until the normal condition is restored.
DTC No.
P0118
E.F.I. water temperature sensor voltage is 4.698 V or more for 0.5 seconds or longer.
(1 trips detection logic)
Suspect Parts:
• Open in E.F.I. water temperature sensor circuit
• E.F.I. water temperature sensor
• ECM
MONITOR DESCRIPTION
The E.F.I. water temperature sensor is used for monitoring a coolant temperature. The resistance of the thermistor integrated into the E.F.I. water temperature sensor changes as the engine coolant temperature changes. The lower the coolant temperature, the greater the thermistor resistance, and the higher the intake air temperature, the lower the thermistor resistance.
The resistance indicates the output voltage from the sensor. The ECM monitors the sensor voltage and use the value for calculating a engine coolant temperature. When the sensor output voltage falls out of the normal operation range, the ECM identifies this as an abnormal condition in the E.F.I. water temperature sensor and stores the DTC.
MONITOR STRATEGY
P0118: Engine coolant temperature sensor range check (High voltage)
Required Sensors/Components (Main)
E.F.I. water temperature sensor
Required Sensors/Components (Related)
-
Frequency of Operation
Continuous
Duration
0.5 seconds
MIL Operation
Immediately
Sequence of Operation
None
TYPICAL ENABLING CONDITIONS
Overlap prohibited DTC
None
TYPICAL MALFUNCTION THRESHOLDS
P0118
E.F.I. water temperature sensor voltage [Engine Coolant Temp.]
4.698 V or more [-46.2°C {-51°F} or more]
OPERATION RANGE
E.F.I. water temperature sensor voltage [Engine Coolant Temp.]
0.357 to 4.688 V [-43.85 to 136.12°C {-47 to 251°F}]

If you car is throwing a code with the ignition in the accessory position you've got a whole other set of problems than a temp sensor dtc.

Do you perhaps mean ON, as in Key On Engine Off? Is the dash on and the check engine light illuminated? Is the temp needle moving? Yes? You're in ON, not accessory.

Anyway, it's a 2 wire circuit from and back to the ECM with an open circuit code, it doesn't get any easier to diag than this. Key ON, temp sens disconnected, you've got 5V on one wire (terminal 2) and ground on the other (terminal 1) if either is missing, check for it at the ECM (connector A36, terminals 29 and 30). If one is missing backprobing the ECM connector then the issue is in the connector (check for terminal tension, defective wire crimps or bent pins) or in the ECM, if both are present at the ECM then your issue is in the harness, find where the wire is cut, if both are present at the temp sensor then your issue is in the connector or the temp sensor, but you've thrown one at it already lol, in this case check for appropriate tension in the terminals, defective wire crimps and bent pins again.

^^This would be my suggestion as well. If there is damage to the harness or plug it will pull the voltage signal down and would be a quick way to figure out if it is the harness, or the ECU itself.

Curious why you didn't prime the normal way holding down the throttle? or just use pressurized oil if you don't want the crank to spin on a newly built engine

have you tried reseting ECU by disconnecting battery?

Also the EFI water temps sensor is next to the Crank sensor on the harness, I'm assuming you pulled out the right one

Okay im dumb. The plugs for the knock sensor and temp sensor are the same so swapped the 2 and no more codes. Rad fans dont come on anymore. All is good.

Just following my built block instructions is all. I got no problems cranking to prime the engine. Also, dont wanna break stuff....again. =P

Shit happens.


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Yea i pulled out the multimeter and started to check. Everything was correct but my checking was cut short because i noticed that the plugs of the knock sensor right under the coolant temp sensor are the same plugs. So i swapped the 2 plugs and no more codes.

Making mistakes is ok, forgetting to mention all your codes isn't. ;)

Can you post a picture of the plugs and sensors? I'm getting ready to wire up and fire up my new engine and want to make sure that I don't have the same issue.

I only did the plugs unfortunately. But i do have a pic of the coolant temp sensor outside of the water pipe.
i think for the sensors you'll figure it out. The knock sensor and temp sensor doesn't look alike at all. only the connectors from the engine harness.

Thanks. I'll double check mine. I find it odd that there are sensors that close together that have the same plug. Every connection that I've seem so far has a specific shape to minimize the chance of mixing them up.

Yea not sure why that is. On the harness i believe theyre right next to each other.
Here are some shitty pics of the coolant temp sensor plug. So just reference the first 2 pics of the plugs i have and you’ll figure it out