electrical woes
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
electrical woes
I have a 1993 in my shop. After a heads/cam swap it has developed curious electrical gremlins.
1)Ect guage(the digital one) reads either lo or 142 deg. Runs like chit.
2) outside air temp reads at least 40 deg higher than it really is.
The Ect is new. All chassis grounds/eng grounds have been confirmed less than 0.4 ohms. Checked all pins from ecm to their respective sensors, no shorts,no open circuts.
I can jumper the ect plug and it does not give me 266deg like it should. I can unplug it and it still reads 142.
I can ground out the yel wire, nothing happens.
I have tried replacing the ground loops in the harness, as some of them looked weathered.
but still nothing.
I thought I had it nailed earlier, as I could get it to go from fine, to dead by yoinking the harness around near the oil temp sending unit. Pull it out of there, unwrap and inspect/test. All wires are fine/undamaged/not shorted. Im out of Ideas.
the ecm works fine in Bruce's car. the harness checks out. What gives?
Anyone have a similar problem?
1)Ect guage(the digital one) reads either lo or 142 deg. Runs like chit.
2) outside air temp reads at least 40 deg higher than it really is.
The Ect is new. All chassis grounds/eng grounds have been confirmed less than 0.4 ohms. Checked all pins from ecm to their respective sensors, no shorts,no open circuts.
I can jumper the ect plug and it does not give me 266deg like it should. I can unplug it and it still reads 142.
I can ground out the yel wire, nothing happens.
I have tried replacing the ground loops in the harness, as some of them looked weathered.
but still nothing.I thought I had it nailed earlier, as I could get it to go from fine, to dead by yoinking the harness around near the oil temp sending unit. Pull it out of there, unwrap and inspect/test. All wires are fine/undamaged/not shorted. Im out of Ideas.
the ecm works fine in Bruce's car. the harness checks out. What gives?
Anyone have a similar problem?
Melting Slicks
Joined: Sep 2003
Posts: 3,474
Likes: 1
From: 1
I'm gonna talk to our P.E. Electrical engineer tomorrow and see what he thinks.
-> does the outside air temp sensor go apeschit and fix itself at the same time as the coolant temp sensor?
-> If so, does the outside air temp sensor use a chasis ground?
-> does the outside air temp sensor go apeschit and fix itself at the same time as the coolant temp sensor?
-> If so, does the outside air temp sensor use a chasis ground?
Last edited by Darkgh0st; Sep 2, 2005 at 12:15 AM.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
Originally Posted by Baldturbofreak
1)Ect guage(the digital one) reads either lo or 142 deg.
142 Celsius=288 Fahrenheit.
With the ECT plug disconnected and the ignition on, do you measure at the connector around 5 volts from the yellow wire to the negative of the battery terminal?
Do you measure the same voltage when you measure from the Yellow wire to the Black wire?
With the ECT plug disconnected, what resistance do you measure across the two pins on the ECT sensor?
Do either ECM DTC 14 or 15 set after the engine has been running?
Do you have a scan tool or scanner software to read the ECT sensor?
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
Im pretty sure it reads deg F when in english mode. I will try both settings.
I get 4.5 v at the pin
I havent measured resistence across the two.
Tried another ect sensor.
Im ready to run new wiring for the sensors.
I get 4.5 v at the pin
I havent measured resistence across the two.
Tried another ect sensor.
Im ready to run new wiring for the sensors.
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
there is no resistance,but not open loop, between the two pins when it's on.
For sure it's reading 142F not C.
I dunno maybe it is the ecm. Doesn't explain why it works in another car though. Problem is so intermittent I can't really count on anything. But Im Certain there is no shorts on circut 410 (yel wire for ect).
Im going to try another ecm in this car. Hopefully that solves it.
For sure it's reading 142F not C.
I dunno maybe it is the ecm. Doesn't explain why it works in another car though. Problem is so intermittent I can't really count on anything. But Im Certain there is no shorts on circut 410 (yel wire for ect).
Im going to try another ecm in this car. Hopefully that solves it.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
If the ECT sensor is reading 142F, it's resistance should be around 667 ohms. To confirm this, disconnect the ECT connector and with a ohm meter measure across the two pins of the ECT sensor. It should measure close to 667 ohms.
Here are some resistance values of the ECT and what temp. they should display.
212 F = 177 ohms
194 F = 241 ohms
176 F = 332 ohms
158 F = 467 ohms
140 F = 667 ohms
122 F = 973 ohms
113 F = 1.188k ohms
95 F = 1.802K ohms
86 F = 2.238K ohms
77 F = 2.796K ohms
68 F = 3.520K ohms
41 F = 7.280K ohms
32 F = 9.42K ohms
-40 F = 100.7K ohms
Here are some resistance values of the ECT and what temp. they should display.
212 F = 177 ohms
194 F = 241 ohms
176 F = 332 ohms
158 F = 467 ohms
140 F = 667 ohms
122 F = 973 ohms
113 F = 1.188k ohms
95 F = 1.802K ohms
86 F = 2.238K ohms
77 F = 2.796K ohms
68 F = 3.520K ohms
41 F = 7.280K ohms
32 F = 9.42K ohms
-40 F = 100.7K ohms
Melting Slicks
Joined: Sep 2003
Posts: 3,474
Likes: 1
From: 1
Originally Posted by Hooked on Vettes
If the ECT sensor is reading 142F, it's resistance should be around 667 ohms. To confirm this, disconnect the ECT connector and with a ohm meter measure across the two pins of the ECT sensor. It should measure close to 667 ohms.
Here are some resistance values of the ECT and what temp. they should display.
212 F = 177 ohms
194 F = 241 ohms
176 F = 332 ohms
158 F = 467 ohms
140 F = 667 ohms
122 F = 973 ohms
113 F = 1.188k ohms
95 F = 1.802K ohms
86 F = 2.238K ohms
77 F = 2.796K ohms
68 F = 3.520K ohms
41 F = 7.280K ohms
32 F = 9.42K ohms
-40 F = 100.7K ohms
Here are some resistance values of the ECT and what temp. they should display.
212 F = 177 ohms
194 F = 241 ohms
176 F = 332 ohms
158 F = 467 ohms
140 F = 667 ohms
122 F = 973 ohms
113 F = 1.188k ohms
95 F = 1.802K ohms
86 F = 2.238K ohms
77 F = 2.796K ohms
68 F = 3.520K ohms
41 F = 7.280K ohms
32 F = 9.42K ohms
-40 F = 100.7K ohms
Good info. This should prove if the ECM is messed or not.Make sure you measure the pins @ the harness too
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Thread Starter
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
Ive already looked into all of that. Pretty much everything there is in the GM tech manual. I'll call bruce tomorrow and see if he will bring his ecm over. In either case, I think I'll put on on order. I can see no other possibility.