I have a 93Z, Hot cam, GM 1.6RR's, 3" Corsa exhaust, air foil and Gm's cold air intake with K&N type filters. A DTC of 114( ECT) was set along poor driving, poor idle and hard starting. I replaced the coolant sensor only to see the DTC of 114 appear again. Further testing showed only 0.54 Volts to the sensor when the GM manual calls for 1.5 V, key on, engine off, at the pin on the ECM. Does this mean that the ECM is bad? Any help would be helpful. Thanks, Ted

 

No such thing as a 114 on '93 F-Body OBD1, did you use the paperclip method. If you took it to a parts place odds are they messed up when it comes to ODB1. Pull the IAT connector w/key on you should have +5V on one lead 0V on the other. Meter ohms between the two terminals in the sensor here is a chart. http://shbox.com/1/4th_gen_tech2.html#ect

 

Thank you for responding to my cry for help. I used the paper clip method to flash the D.T.C's.
I have a Actron scan tool, the one with the removable cartrige CP #9110, that is not working, thus the paper clip. I have used the method that shoobox describes to no avail. That method is described in my G.M, service manual. The ohms correspond th the chart/temp. The service manual says to look for 1.5 volts DC at the yellow wire at the Temp sensor. Key on, engine off. My voltage reading following this method shows 0.54volts on my DVM. Tracing the wire back to the ECM, I record a DC Voltage that Varies little perhaps 1/10 Volt, at the pin at the ECM. Seems strange that only one circut is affected. Is there a way to check the whole ECM?? Thanks again, Ted

 

I'm still not clear, did you get a DTC 14 (not 114) by using the paper clip method. There s/b 1.5-2.0 volts on the yellow wire with the engine at 185-203* F. At that time the resistance of the sensor s/b about 240 ohms. Make sure you are reading the voltage between the yellow and black wire (PCM ref ground) not yellow and chassis ground. Usually PCM failure is pretty rare, but it's possible the +5V reference circuit to this sensor could be bad within the PCM. If you had another '93 ECM to swap, no need to start the car just plug it up turn on the key and check the voltage, it s/b much higher than 2.0 on a cold engine. Would be nice to get your scanner going to see what temp the PCM is seeing.

 

I checked with Actron, they want as much to look at my scanner, $76.00 + 10.00 shipping+ parts, if they can fix it. )n line they are a 159.00 $ item. I hate to do it but I need to diagnose this properly, and not throw parts at it. In the meantime, Ill be looking for a 92-93 computer to borrow. Thanks again

 

If you have a laptop you can buy a cable for $65-90.00 and download FreeScan or TTS DataMaster for 20 free logs..

 

where can you get the cables? are they the same ones you use for lt1 edit? where can you get the softwhere?? you can only use it 20 times?

 

TTS DataMaster:

http://www.ttspowersystems.com/

Cable:

http://www.akmcables.com/

 

I will Download the TTS Datamaster.
I checked Circut #4 and circut # 5 both show =12.6 volts to ECM. Ground wire(s) from ECM to ground "ok". Coolant sensor OHMS correspond with coolant temp.
ECM voltage to coolant sensor is 0.54 measured at ECM. The G.M manual calls for Voltage to be 1.5 volts to the sensor with key on and engine off at the sensor.
Thank you, Ted

 

Voltage on the CLT sensor circuit varies with temperature. It will read 1.5-2.0 V with a coolant temp of 185 - 205*F. Is that what the coolant temp is when you are getting 0.54V?

When you take the connector off the sensor, do you get 5.0V across the connector pins?

 

Engine not run for 8 hours or more. Ambient air Temp. 70 degrees F. Coolant temp. about the same. Ohms across the coolant disconnected from harness =285. Voltage to the sensor =0.50 Volts, key on, engine off. Voltage to the ECM =12.6 Volts on both circits.

 

I'll try this one more time. Key on, pull the harness connector off the coolant temp sensor. Measure the voltage across the two pins in the the connetor. What is the voltage? If its only 0.50V with the connector DISCONNECTED you have a problem with the PCM. It's supposed to supply 5.0V (disconnected).

If your coolant temp is 70*F, the resistance of the sensor DISCONNECTED should be about 3,500 ohms. A resistance of 285 ohms would correspond to a coolant temperature of about 185*F.

Somehow, your measurements sound screwed up. Did you read Shoebox's instruction link, that bobdec posted? Its all spelled out very clearly in there.

 

Thank You, I know that we are having a communication problem. I have been trying to say that the Voltage to that coolant sensor, with sensor disconnected, AT the electrical connector to that sensor is 0.50 Volts DC - Key on engine off.
The 285 I mentioned should have read 2850.
Thanks again for trying to help, Ted

 

OK I got it straight now. Your +5V reference voltage from the ECM to the sensor reads .50 volts. If you truly have the meter on the correct scale (saying this because .5 and 5.0 are coincidental readings) checked the wire back and the voltage is bad at the ECM then most likely the +5V circuit driver for the temp sensor is bad in the ECM. Next step is to pick up another or try swapping. Some of the tuner sponsors may test the circuit for you if you send it in for a replacement and tune.

 

Bobdec, thank you for that information on that driver circut to the coolant sensor. I have cchecked th Voltage out of the ECM, To the ECM using different meters and the 0.5 Volts DC is correct, unfortunatly. You hit the problem area in the computer exactly!!
Thanks again. I searching for a replacement today.Thank you. Ted