Need ECU pin reading specs for cold engine. I have been able to find what readings I should see when back probing the ECU when the engines warm, but what about cold?

I cant get my engine to start, so I cant warm it up and I am trying to fix a flooding issue.

Perhaps someone can give feedback on the following readings on a S4 Turbo?

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pin 2M-Pressure regulator control:


2v ignition on
8v during cranking (should be 2v when cranking) and 12v at idle.

Cause? Symptoms?
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pin 2O-switch solenoid valve

2v ignition on (should be 12v). The TPS is reading 1v.

Cause? Symptoms?

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pin 1H-water temp switch

10v ignition on. (found switch was bad so spliced wires) now reads 0v

Should be less than 1.5v but is zero volts ok?

Is 10v when open normal or a sign of a short somewhere?

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i know these are advanced questions and a lot of them, but any help would be very appreciated.

THANKS!

 

************************************************** ********************pin 1H-water temp switch

10v ignition on. (found switch was bad so spliced wires) now reads 0v

Should be less than 1.5v but is zero volts ok?

Is 10v when open normal or a sign of a short somewhere?
************************************************** ****************

No voltage means there's an open wire b/t the water thermo switch and the ECU. If this happens the ECU defaults to a temperature reading of 176* F.

IF it defaults to that temp, then a COLD engine will be difficult to start because not enough fuel is being injected. Once hot, the engine will start normal. Only cold starts will be difficult.

 

************************************************** **********************pin 2M-Pressure regulator control:


2v ignition on
8v during cranking (should be 2v when cranking) and 12v at idle.

Cause? Symptoms?
************************************************** *********************

During cold starting this solenoid matters not imho. Not a twit bit. I'm not sure what your asking about it, but it matters not during a cold start. Nadda.

 

************************************************** **********************pin 2O-switch solenoid valve

2v ignition on (should be 12v). The TPS is reading 1v.

Cause? Symptoms?
************************************************** *********************

Not a player in any sense during starting. By the way, with a COLD engine, the TPS should NOT be reading 1vdc. It normally will be higher. How high? Depends on how cold it is and how much the water thermowax is opening the throttle plates.

On the whole, not a player at all during starting. It's ACV related which is emissions related.

I really don't understand why its reading 2v or less. That means the ECU is putting a gnd on the solenoid. Shouldn't happen if the TPS is at 1vdc.

 

With good wiring, pin 1H should be reading in the 2-3vdc range. Depends HOW cold, cold is.

I mean, voltage leave 1H, heads for the water thermo sensor, passes thru and comes out the other wire which is a gnd wire for all the sensors in the engine bay. Eventually makes its way back to 2C on the ECU.

 

Back probe 3B and momentarily put the key to Start. Did you see 12vdc momentarily?

What are you seeing on pins 3F,3H, 3C and 3E. Should be batt voltage.

Here's a dandy. Backprobe 2A and see what you get. Should be 4.5 plus volts. Less than say 2vdc, then ECU sucks/bit the dust or??????

I'd check for batt voltage on the small, two socket plug at the Lead coil assy. It's black/yellow wire should have batt voltage. Don't be messing with the other wire in that plug.

 

I should probably mention that I removed the thermo wax when I modded the TB. If the TPS should read above 1v, anyone know how much. I followed the steps of TPS calibration, maybe I missed something?

HAILER, thanks for all the feedback. I will check those other pins and post back with the results.

 

Some info on starting:

 

Have you checked every single solitary fuse in the car--with a multimeter?

 

Ok, so I checked all pins that I was recommended to, they all test good. I tried to start the car again today and I think I am close. The car was badly flooded, now I am past that and able to get it to start with starter fluid for a few seconds.


Check out an old thread I just updated for more info. Thanks for the help everyone!

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/help-rough-idle-smoke-new-motor-same-problem-482517/