'93 Accord EX w/auto, 190K miles

Tuesday morning on start-up I got the flashing check engine light and flashing D4. Connected the SC and got a code 6 which the shop manual indicates is a problem in the Engine water temperature circuit. First thing I do is reset the ECU and the flashing CEL and D4 are gone. Four days go by... no flashing codes. This morning I start the car and the codes back. Reset the ECU again, but now the D4 comes on with the CEL for 2 seconds on start-up and then both go off. I'm concerned about the D4... what fault is that indicating???

I need to check the resistance of the water temperature sensor, but can't get the connector off. Access is very tight. Any suggestions???

Appreciate any help or guidance.

 

Which light flashed the code 6 when you shorted the connector?

 

The check engine light flashed code 6.

 

Been wrong before and will be again. I thought the D4 light coming on for a few seconds (just like the CEL) was/is normal-bulb check.

Sorry-don't have any great tips on getting the connector off. EDIT: got kids with small hands that may be able to help?

 

First are you accessing the sensor slightly below and in front of the distributor? I ask because it looks fairly accessible.

These pinch-type connectors can be difficult to remove. I've had some success using pliers to pinch and pull. However, it is easy to over-squeeze and damage the connector.

Suggest first trying to spray some WD40 into the connector to lube. Then clean/wipe carefully and try again to pinch/remove. Also a small screwdriver to pry gently at the gap between the connectors can sometimes help.

You should download or perhaps you have a shop manual to provide guidance on measuring resistance of the thermister to check it's accuracy. The manual check procedure says resistance should be 200-400 ohms, but that will only be true if coolant temperature is ~ 176-212 degF, with fully warmed engine which procedure also calls out. (see resistance-temperature chart).

good luck

 

Thank you for the suggestions. Got the pinch connector off with the little help of a screw driver. Warmed up the engine until the radiator fans cycled. Checked the resistance of the coolant temperature sensor and got right at 200 ohms. Manual says it should measure 200-400 ohms. So it should be OK. Moving down the troubleshooting chart...a voltage check of the yel/grn wire of the connector to ground with the ignition switch on is 5V. Checking the voltage across the connector yel/grn to grn/wht also 5V. Last step says to replace with known-good ECU...which I don't have. Does this mean the ECU is bad?

 

I would replace the sensor. It is close to being out of range at 200 ohms.

 

If code comes back, suggest disconnecting connector from ECU w/ the ECT sensor leads and checking the resistance at that point. If it shows open or short, then there's a wiring or connector problem somewhere. Start at the connector to the sensor and trace towards the ECU, checking wires separately to find the fault.

good luck

 

Thanks for the suggestions...

I'll continue to monitor... watching for a recurrence and pick up a replacement ECT sensor.

With the ECU codes are cleared, what should the check engine light be doing if the service check connector is still installed??? I'm getting a continuous check engine light. Not flashing, but not off either. What should I expect???

 

With the SCS shorted, the CEL will stay on solid, if there's no errors. (Confirms that you shorted the proper connector...)