So, it's been a while but I finally got around to replacing the fuel injectors just a few days ago. This, along with the new fuel pump, has made the truck run almost like new - that is until the radiator blew!

Two days ago, all of the sudden the upper radiator hose gave way and blew coolant all over the truck. My temperature gauge hit 260 degrees before I could get the vehicle over to the shoulder and off the road. Well, I let the engine cool and replaced the hose just to find out the radiator was cracked and leaking.

So, I replaced the radiator this morning as well as the MAP sensor (the gasket for the MAP sensor was cracked - noticed it when I changed out the injectors). And when I got everything back together I noticed the CEL was on. I pulled the codes and came up with P0117.

Would this error some how be related to the rough idle I'm getting now? It was running fine until the radiator issue. Now it's idling like I have the old poppet injectors back in the motor.

 

OBD-II Trouble Code Technical Description

Engine Coolant Temperature (ECT) Circuit Low Input

Collision



What does that mean?

Repair



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The ECT (Engine coolant temperature) sensor is a thermistor located

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in the engine block or other coolant passage. It changes resistance

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It's usually a two wire sensor. One wire is a 5 volt reference from

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PCM (Powertrain Control Module) and the other is a ground supplied

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from PCM.

As the temperature of the coolant changes, the resistance of the sensor changes. When the engine is cold, the resistance is high. When the engine is warm, the resistance is low. If the PCM detects a signal voltage lower than the normal operating range of the sensor then P0117 code will set.

Symptoms

Potential symptoms include:

MIL (Malfunction Indicator Lamp) illumination Poor fuel economy Poor drivability Engine may run rough or blow black smoke out the tailpipe May not idle May start and then die

Causes

Potential causes of the P0117 code include:

Bad ECT sensor Short to ground on ECT signal circuit Faulty or damaged connectors Wiring harness damaged Loose terminals at ECT or PCM POSSIBLY an overheated engine Bad PCM

Possible Solutions

Since this code is for an abnormally low signal to the PCM from the ECT, the PCM saw a excessively "hot" condition in the engine coolant. This could be due to faulty ECT sensor or wiring, but it could, conceivably, be caused by an overheated engine.So if your engine was overheated diagnose that first. Having said that here are the possible solutions:

Using a scan tool, with KOEO (Key on engine off) check the ECT reading on the display. On a cold engine the ECT reading should match the IAT (Intake Air Temperature) sensor reading. If it doesn't, replace the ECT sensor.

1. If the ECT reading is showing an excessively hot reading, for example more than 260 deg. F, then unplug the ECT sensor. This should cause the ECT reading to drop to the extreme cold reading (around -30 deg.F or so). If it does, replace the sensor, because it's internally shorted. If it doesn't change the reading, the check for a short to ground on the signal circuit of the ECT wiring. It could be that the two ECT wires are shorted to each other. Look for any chafing or melted wiring. Repair as necessary.

a. If you can't find any wiring problems and the ECT reading doesn't drop to the extreme coldest when unplugged, then, check for voltage coming out of the PCM on the signal wire's pin at the PCM connector. If there isn't any voltage, or it is low, then the PCM may be bad. NOTE: On some models it is possible for the 5 Volt reference signal to be temperarily shorted. This can happen if an engine sensor internally shorts the 5 Volt reference. Since the 5 Volt reference is a "shared" circuit on many models, this will cause it to be abnormally low. Usually, though this will be accompanied by several other sensor codes. If you suspect that may be the case, unplug each sensor until the 5 Volt reference reappears. The last sensor unplugged is the offending sensor. Replace and recheck the signal wire from the PCM connector

2. If the scan tool ECT reading seems normal at this time then the problem may be intermittent. Use a "wiggle" test to manipulate the wiring harness and connectors while watching the ECT reading on the scan tool. Repair any wiring or connectors that are loose or corroded. You could check the Freeze frame data if your scan tool has that function. It will show the ECT reading when the failure occurred. If it shows the reading to be at the hottest extreme then replace the ECT sensor and see if the code reappears.

 

Thanks but after replacing the sensor, I'm still getting a rough idle.

This is so frustrating. I had this vehicle running smoothly for two whole days. Now, the engine gets a little hot, it's back to a rough idle.

I unplugged the IAT to see if that made a difference and it did. Or, at least the idle was smooth in park and drive. The only problem I saw as the high idle (900ish rpms) while it was parked.

Any more suggestions?

 

You need to figure out why?Either bad thermostat or possible water pump.Did you blow any gaskets from the engine getting so hot?
Did your pcm get coolant sprayed on it?I would check all your electrical connections under the hood wipe them off with dry cloth.Use a blow drier make sure all the contacs are dry.Clean all your sensors also.

 

The thermostat is new and I went ahead an bought a new water pump this morning (noticed it was leaking on the backside ). As far as blowing a gasket, I don't think so. There wasn't much coolant being sprayed over the engine compartment. It stayed mostly near the ruptured hose. In fact, the more I think about it, the more I'm leaning toward just a bad hose.

I'll check all the connections again. I could have over looked something in my frustrated manner.