DIY PGMFI Diagnostics - Code 6 ECT

**ECU-MAN** · 24-05-2007 12:34 AM

Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!

No part of this DIY is to be reproduced with out acknowledgment of the site and author it came from, ie me and ozhonda.com. Do not rip parts off and claim them as your own.

ECT sensor "Engine Coolant Temperature" also known as TW "Temperature Water" Sensor and "CTS" Coolant Temperature Sensor.
The ECT sensor is commonly located on the side of the head, under the Distributor. Not to be confused with the thermo fan switch located on the thermostat housing or the top hose housing. Also not to be confused for the Engine Temperature Sender for the Temp Gauge, Also located on the side of the head under the distributor but only has 1 wire. ECT has a two wire connector.

The ECU monitors the ECT to determine Injector Duty, Ignition Timing and Idle speed.

Bellow is a picture of an ECT sensor on a F22B1. note the 3 other sensors near the ECT

Blue arrow = ECT
Red arrow = Temp Gauge Sender
Green Arrow = Thermo fan after run Sensor ( not thermo fan switch )

Aim:

Diagnose code 6.

Required:

Basic Testing

- Digital Multi Meter
- paper clip

Symptoms

For a faulty ECT sensor to trigger code 6, you will more than likely get the engine light come on and the car will go into limp mode, Limp mode is a preset fuel and ignition map running on a backup processor in the ECU. Limited to about 3500rpm and a rich mixture to protect the engine the engine will run, but not the best. Common cause for code 6 is a faulty ECT or open circuit in the wiring back to the ECU. 3rd party ghetto resistor hacks can cause problems.

Basic Test

- Perform a Visual inspection and make sure the ECT sensor is Connected

ECT Sensor Pin out Picture

wire side of connector

**** Voltage Test ****

Set your multi meter to DC Volts ( 20v scale )

Step 1 ( Reference Voltage test )

Note: The Sensor signal wire could vary from Pin 1 or Pin 2, your best bet is to pick the red/white wire.

Check the ECT sensor for its Reference Voltage from the ECU, Note that the reference voltage wire is also the signal wire. Connect the Black Lead from your multi meter to the chassis for a good ground. Back probe* the ECT with the Red lead to Pin 2 of the ECT sensor while the sensor is disconnected.

KOEO* you must get 5v

If you get 5v proceed to step 2,

if you do not get 5v, try Pin 1 of the ECT ( incase its wired differently ) repair open or short circuit to ECU from Pin 2 of ECT (red/white wire) to the bellow ECU Pin ( also see continuity test bellow )

OBDO = C6
OBDI = C13
OBDIIa = D2
OBDIIb = C26

If you do not get 5v from the ECU pin above, replace the ECU.

STEP 2

Check ECT sensor for a good ground. Leave your Red lead from the above test on Pin 2 (red/white wire) of the ECT. Back probe your Black lead into Pin 1 of the ECT. ( Blue or Green/blue wire )

KOEO* you must get 5v

If you get 5v proceed to step 3,

if you do not get 5v, repair open or short circuit to ECU from Pin 1 of ECT to the bellow ECU Pin ( also see continuity test bellow )

OBDO = C12
OBDI = C22
OBDIIa = D11
OBDIIb = C18

Leave your Black lead of the multi meter as is and move the Red Lead from Pin 2 of the ECT to the positive battery terminal. You should get 12v. If not, repair the wire between Pin 2 of the ECT and Pin listed above to the ECU.

STEP 3

Check the ECT Signal. Connect the Black Lead from your multi meter to the chassis for a good ground. Back probe* the ECT with the Red lead to Pin 2 ( red/white wire ) of the ECT sensor while the sensor is connected.

KOEO* you should get 3.2v to 4v with a cold engine. 0.6v with a hot engine
KOER* With a cold engine your voltage should start at 4v and drop as the engine warms up to about 0.6v when the engine has reached operating temperature.

as engine temperature increases ECT voltage decreases

If you do not get a signal on Pin 2 but just get 5v, replace the ECT sensor with a known good one and retest. If you do get a signal at Pin 2, then check the signal at the ECU end.

OBDO = C6
OBDI = C13
OBDIIa = D2
OBDIIb = C26

If you get a good signal at Pin 2 ( red/white wire ) on the ECT and no signal on the above ECU Pin, repair the Open circuit between the above ECU Pin and Pin 2 ( red/white wire ) of the ECT.

***** Its is always best to check sensor inputs at the ECU side *****

**** Continuity Test ****

Set your multi meter to continuity. This setting is mostly a picture if a sound .))) when you touch the Red and Black leads together on your meter it should beep.

STEP 1

make sure the Ignition is off and unplug the ECT Connector and the ECU Connectors for this test

Continuity test between ECT Pin 1 ( blue or green/blue wire ) and ECU, Connect your Red multi meter lead on the ECT Pin 1, Back probe* the Black multi meter lead on the ECU Pin bellow that suits your car.

OBDO = C12
OBDI = C22
OBDIIa = D11
OBDIIb = C18

your multi meter should beep and read short or 000.0ohms.

STEP 2

make sure the Ignition is off and unplug the ECT Connector and the ECU Connectors for this test

Continuity test between ECT Pin 2 ( red/white wire ) and ECU, Connect your Red multi meter lead on the ECT Pin 2, Back probe* the Black multi meter lead on the ECU Pin bellow that suits your car.

OBDO = C6
OBDI = C13
OBDIIa = D2
OBDIIb = C26

your multi meter should beep and read short or 000.0ohms. Place the black multi meter lead on a good ground source. You should not get beeping, this is testing for short to ground.

**** Resistance Test **** Set the multi meter to ohms ( 1M scale )

Unplug the ECT sensor, connect your Red multi meter lead to Pin 1 of the ECT. Connect your Black multi meter lead to Pin 2 of the ECT.

with a cold engine, the resistance should be about 2.7k ohms
with a warm engine, the resistance should be about 215k ohms

as engine temperature increases ECT resistance increases resulting in the signal voltage decreasing.

A good test for the ECT is to remove it from the car, put it in boiling water and monitor its resistance as the temperature changes. The resistance should change with out dropouts or glitches.

* Notes

KOEO = Key On Engine Off

KOER = Key On Engine Running

Back probe the sensor, use a paperclip and push it into the connector then touch/clip your multi meter lead to the paper clip

Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!

**OzSir2** · 11-02-2008 08:58 AM

I followed some of your instruction and think I've got a bad sensor. I first checked that 5V and earth was coming from the plug. I didn't bother with the testing at the ecu because there seemed to be more of a pattern to when the engine light came on...so I did the resistance checks. You mention to have the MM set at 1M scale but mine doesn't...but when engine hot I got a few variable readings around 150 and once 194 (but never 200 or more) on the 200ohm scale and 216 on the 2000k ohm scale when cold. I have no trouble cold starting...only hot starting...and the engine light only comes on when warmed up. So is this because the sensor's resistance is dropping below the normal and the ecu thinks the sensor is not there at all. In other words my sensor is stuffed?

**ECU-MAN** · 11-02-2008 01:36 PM

its doe ssound like when its warms up the sensor goes out of range and the ECU freaks out. Im not sure if you read this part above

"A good test for the ECT is to remove it from the car, put it in boiling water and monitor its resistance as the temperature changes. The resistance should change with out dropouts or glitches."

but thats a good way so see what is happening.

if your connection to the ECT was good when testing then it sounds like you have a bad ECT