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ecu drama?

markovr

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07vessv 94vr .04vz wgn,93vp wgn,82 vhV6 wgn 88 vn
Have had the v6 engine in the vh running rough lately and using a lot of fuel...tried the codes and it has code 13 up so we put the scan tool on and it reads 4.42 mv and doesnt change with throttle movement...so we changed the o2 sensor but the scan tool still reads 4.42 mv. Checked the wiring and it all tests out. would you change ECU next?
 

Circlotron

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ECU is $40 at some wreckers, so why not. If not the ECU then you've got a spare, just like me :nopity:
 

SavVYute

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Check the wiring loom connection to the ECU?
 

FXST01

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What does the O2 sensor read at cold and at hot?
 

Cheap6

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If it's actually 442mV I'd buy that as the cold voltage.

Otherwise, back probe the O2 sensor at the sensor and check the voltage wrt a known good earth and see if you get the oscillation or at least compare the voltage from there and at the ECM. Also try artificially inducing rich and lean and watch the O2 voltage. Removing a vacuum hose and spraying carb. cleaner or starting fluid into the intake will do it.
 

markovr

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07vessv 94vr .04vz wgn,93vp wgn,82 vhV6 wgn 88 vn
Ok put a new ecm in and it didnt fix the problem. The diagnostic program I am using is efi live and it seems to buffer and have a second delay on its readings but when in the window showing a dial layout show the o2 sensor staying at not much past 0 v. Proved the purple wire for the o2 sensor was good back from sensor to the ecm plug but havent proved the negative yet. Still get code 13 in fault code.
 

Cheap6

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The delay might be that the ECM just doesn't update the ALDL data all that quickly, particularly if it's the 1227808. (Is it?)

No voltage out of the sensor - something up to 1000mV? It will have to be hot though. It will still generate voltage if it's not connected so you might want to try it that way too.
 

markovr

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07vessv 94vr .04vz wgn,93vp wgn,82 vhV6 wgn 88 vn
I think I found it finally ....its my wiring but surely I could be forgiven ...why anyone would make the black wire positive(its called signal ) I cant fathom it really ...in most automotive circuits black is negative but I found this while I was searching for answers

Since we installed the new engine we have had the sensor wired backwards since I extended the wiring I didnt take too much notice of the plug wiring but assumed the purple internal wire went to the grey of the sensor and the black wire went to the black....no wonder the sensor has no output.....
 
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