97 Legacy Outback 2.5 P1502 Code

[TX_Dj]

Fellas,

My buddy's outback overheated the other night, the radiator cap failed.

Replaced that, and also checked the resistances on primary/secondary for the coil pack for another reason, and after putting down the hood, the MIL was lit.

Scanned the code, it's P1502 - claiming "Radiator Fan Function Problem"

Prior in the day, the fans were running perfectly.

Connecting the green self-test leads under the dash results in the fans running find at all 3 speeds.

Anyone have any clue what else can contribute to this code? Even when the car is completely cold and has (we think) cleared codes, it still immediately pops up the P1502 code.

While I was checking the coil, I made sure not to mess with any other harness connections... but it wasn't until after that test that the code started coming up. The fans are fine, the relays are fine, what else contributes to this code?

[TX_Dj]

Nobody?

I want to check the engine coolant temp sensor to see if it's reading out of spec, confusing the ECU... but I can't find the dang thing. I've looked all around where the haynes manual says it should be, and I don't find it. It claims all that's needed to remove it is a deep socket, and I'm not finding anything that might be this sensor in range of some place where you could get a deep socket to it, let alone a rachet without extension for that socket, or without removing the intake manifold.

[green97gt]

youve probably done the simple things like check the connectors/wiring for damage/moisture etc?

as well as check that the fans are not blocked/bound up or something?

and i believe the coolant temp sensor is on the Pass. side(LHD) rear of engine, under intake manifold on the metal coolant crosspipe that sits on top of the block....i think.


http://www.lovehorsepower.com/SubaruDoc ... ensor.html (http://www.lovehorsepower.com/SubaruDocs/CoolantTempSensor.html)

i dont think that a bad coolant temp sensor would throw your code tho.

does your temp guage work?

[ouch1011]

clear the code, see if it comes back. if so, you know the failure is still present and you can continue testing from there.

[TX_Dj]

youve probably done the simple things like check the connectors/wiring for damage/moisture etc?

as well as check that the fans are not blocked/bound up or something?

As per my original post:


Connecting the green self-test leads under the dash results in the fans running find at all 3 speeds.

The fans work fine. The computer thinks there's a problem with the "Fan Function".


and i believe the coolant temp sensor is on the Pass. side(LHD) rear of engine, under intake manifold on the metal coolant crosspipe that sits on top of the block....i think.


http://www.lovehorsepower.com/SubaruDoc ... ensor.html (http://www.lovehorsepower.com/SubaruDocs/CoolantTempSensor.html)

Thanks for the link, that is PERFECT. Neither Haynes nor any other source I've found online could tell me that I needed to remove the intake plenum and remove hoses, they just point an arrow under the intake manifold runner between the PS pump and alternator. That link above is the bomb, thanks for that.


i dont think that a bad coolant temp sensor would throw your code tho.

does your temp guage work?

See that's what I'd think too, unless it's feeding the ECU with a value that's preposterous, like it thinks the coolant temp in 999F or something. I had tested his coil pack primary resistance just before the P1502 code started getting thrown, so now that I know where the coolant sensor is, I have to say it may be plausible that when I disconnected the coil pack, I may have pulled on the harness and wiggled the coolant sensor's wire loose or something.

Instrument cluster temp gauge works perfectly, but according to the haynes manual, there are two sensors- one which feeds the temp gauge, the other which feeds the ECU. It's the one for the ECU I am suspicious of at the moment.


clear the code, see if it comes back. if so, you know the failure is still present and you can continue testing from there.

Immediately. Every time. Thus why I wanted to know where the sensor is, because the fans obviously work fine. It's the only other thing I found on the wiring diagram that could contribute to the code, since the ECU turns the fans on based on the reading from the coolant sensor.

In other news, it seems his thermostat needs replacing also. I'm just hoping we don't have to touch the water pump. Water pump doesn't look like any fun at all on this engine.

[jey]

Thermostat is very easy. Remove the lower radiator hose and the housing for the thermostat and there it is. Make sure you replace it with an OEM part and that the little agitator pin is facing the correct direction.

[TX_Dj]

Thermostats are easy peasy. No trouble there.

And last night, we got it to run both fans while warm, but still there's a code (i don't have a scanner, and autozone was closed by the time we were done). Don't know if it's the same code.

It overheated on him again this morning on the way in to work. The only part of the cooling systems that hasn't been replaced yet is the water pump and radiator.

I'm stumped.

[jey]

Yeah unfortunately you have to remove the timing belt to get to the water pump :( A good mechanic does it when the timing belt needs to be done as proactive maintenance.

[ouch1011]

What kind of driving is happening when it overheats? Highway driving or stop and go? What happens when it overheats? Does it just read high on the gauge, or does a ton of coolant get pushed out into the overflow bottle? Does the heat still blow hot when it overheats? Are the fans running when it overheats? Do the fans blow hot or cold air when it is overheating?

That should help clear up what is happening.