Replaced sensor, ECT code still(and CEL) on

[Denny]

Stump the chumps! JK guys

Soooo I replaced the ECT with a new one from Autozone(Wells part SU201) today and fired her back up. Yes the battery was disconnected, and left disconnected overnight. The CEL still came on and I got the same code, 51.
Also, Chris(HunterVF) noticed that my cooling fan was on even though my coolant temp was on the low side. After that, I noticed it was on anytime I came to a stop(idle). I can't tell if the fan was on during driving due to various other noises causing "interference"
So now I am stumped and would like to know what to do from here...
Thanks all

 

[Rockledge]

If there is an open in the circuit or extra resistance (bad connection, broken wire, etc.) somewhere, that could cause the signal voltage to be too high.

 

[Denny]

I checked the connection and that wire, seemed to be in working order. However, looking at my spare engine, it looks like they're three coolant related sensors, but their connections are slightly different. There's one on top of the block, under the injectors/intake. Then there's another one on a pipe that goes to a hose by the rear head. Are these variations of ECT or something completely different?

 

[DHMag]

the sensor on the hard line is the CELO Switch, Cold Engine Lockout Switch. blocks cold water from passing thru the heater core when engine is cold. also aids engine warming.

 

[SHOketer422]

same thing happened to me, replaced my sensor, had battery disconnected, but still wouldn't get that code to go away, then i disconnected battery again, and pressed the brakes for maybe 30 seconds, its supposed to clear out the keep alive mem KAM i don't know how long that stuff stays alive haha after the battery is disconnected, so who knoows but i'd think yours was clear after one night...dunno, try it, can't hurt...worked for me...

 

[Denny]

Thanks for the info DHMag
Well SHOketer, I should have mentioned I thought about that thing with the brakes. However, I was bleeding the brakes today due to some rear hose replacement and the battery was disconnected so all that keep alive should have been zapped out...darn gremlins

 

[Rockledge]

It's either the ECT itself, the circuit, or the PCM. Nothing else could cause that code to be set. In fact, the pinpoint test is so short for DTC 51 that I can even copy/paste it here for you:

DA10 - DIAGNOSTIC TROUBLE CODE (DTC) 51/118 OR 54/113: INDUCE OPPOSITE DTC 61/117 OR 64/112

DTC 51/118 (ECT) or 54/113 (IAT) indicates that the corresponding sensor signal is greater than the Self-Test maximum. The maximum for ECT and IAT sensors is 4.6 volts.

Possible causes:

-- Open in harness (IAT or ECT).

-- Faulty connection.

-- Faulty sensor.

-- Faulty Powertrain Control Module (PCM).

PINPOINT TEST

l Key off.

l Disconnect suspect temperature sensor.

l Connect a jumper wire between the sensor signal circuit and SIG RTN circuit at the temperature sensor vehicle harness connector.

l Run Key On Engine Off Self-Test.

l Is DTC 61, 64, 112, or 117 present?

Yes
REPLACE suspect sensor.
REMOVE jumper wire.
RECONNECT vehicle harness.
RERUN «Quick Test».

No
REMOVE jumper wire.
GO to «DA11».


DA11 - CHECK CONTINUITY OF SENSOR SIGNAL AND SIG RTN CIRCUITS

l Key off.

l Suspect temperature sensor disconnected.

l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

l Install breakout box, leave PCM disconnected.

l Measure resistance between sensor signal circuit at the temperature sensor vehicle harness connector and Test Pin 7 (ECT) or 25 (IAT) at the breakout box.

l Measure resistance between SIG RTN circuit at the temperature sensor vehicle harness connector and Test Pin 46 at the breakout box.

l Is each resistance less than 5.0 ohms?

Yes
REPLACE PCM.
REMOVE breakout box.
RECONNECT all components.
RERUN «Quick Test».

No
SERVICE open circuits.
REMOVE breakout box.
RECONNECT all components.
RERUN «Quick Test».