Honda Car Forum

I have a 1991 Honda Accord EX with 470000 miles. Lately, I exchanged the
thermostat and code error 6 popping up. Refer to the service manual, it is
coolant temperature sensor. I followed the service manual and measure the
resistance on the sensor when engine warm up with cooling fan on. It is
open compare to spec with few hundreds ohm and I determined that it is the
sensor problem. But when I try to measure the voltage on the sensor
connector and I notice it is 12V instead of 5V mention on the manual. After
that, I measured another good same year and model vehicle from my friend and
it is 12V output on the sensor connector and the sensor is open when engine
hot. On my friend car doesn't has the error code coming out. Would anyone
has the similar problem and recommend which area I can check to solve this
problem.



Thanks



Eric

"Eric" <ewong1@motorola.com> wrote in
news:ffo8sh$9c6$1@newshost.mot.com:

> I have a 1991 Honda Accord EX with 470000 miles. Lately, I exchanged
> the thermostat and code error 6 popping up. Refer to the service
> manual, it is coolant temperature sensor. I followed the service
> manual and measure the resistance on the sensor when engine warm up
> with cooling fan on. It is open compare to spec with few hundreds ohm



I don't know what kind of manual you're using, but it's wrong.

The resistance should be checked with the ignition OFF and the connector
UNPLUGGED. You check the resistance between the pins of the sensor itself.

You should check resistance both engine hot and engine cold.

Full-hot, you're looking for about 200-400 ohms. Cold, the resistance
should be about 10,000-20,000 ohms.



> and I determined that it is the sensor problem. But when I try to
> measure the voltage on the sensor connector and I notice it is 12V
> instead of 5V mention on the manual. After that, I measured another
> good same year and model vehicle from my friend and it is 12V output
> on the sensor connector and the sensor is open when engine hot.



To check the voltage, you turn the ignition to "II" (engine can be any
temperature), unplug the connector from the sensor then probe for voltage
between the two wires in the connector.

Do all the checking procedures correctly and see what you get.




--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

Eric wrote:
> I have a 1991 Honda Accord EX with 470000 miles. Lately, I exchanged the
> thermostat and code error 6 popping up. Refer to the service manual, it is
> coolant temperature sensor. I followed the service manual and measure the
> resistance on the sensor when engine warm up with cooling fan on. It is
> open compare to spec with few hundreds ohm and I determined that it is the
> sensor problem. But when I try to measure the voltage on the sensor
> connector and I notice it is 12V instead of 5V mention on the manual. After
> that, I measured another good same year and model vehicle from my friend and
> it is 12V output on the sensor connector and the sensor is open when engine
> hot. On my friend car doesn't has the error code coming out. Would anyone
> has the similar problem and recommend which area I can check to solve this
> problem.
>
------------------------------

I don't know if it will help, but did you fill the reservoir to MAX (per
the owner's manual) when you were finished with the cooling system? The
'91 can trap lots of AIR and there's no way to displace it if the
reservoir isn't full. If the coolant is low (air) the sensor will never
get immersed and so you may get error codes. Bleeding instructions are
at www.tegger.com , I expect.

'Curly'