Scanmaster Output

I've been reading up on PCMs lately and trying to learn as much as I can about EFIs. Fortunately, I bought a car with a Scanmaster LT-1 mounted on the dash, so I've had lots of opportunity to observe.
I know that there are at least 19 cells, but my Scanmaster reads Cell 16 at idle and 18 under any throttle...and that's it. Where are the other cells?
Also, at idle, my left BLM reads 160 while the right reads ~135.
In cell 18, they both approach the optimum 128.
Left integrator and right integrators both hover around 128 at idle and the left reads ~20 higher than the right in cell 18.
Injector pulse width for the left is 2.9-3.0 at idle and the right injector reading is 1.9-2.0.
Any ideas as to why they aren't balanced?
I suspect that I have a bad plug wire on the right side; would that account for the differences? Could the right side be leaning out because of a dead cylinder?

A bad plug wire on one side of the engine can affect the blms of the other side in the opposite direction. Another possiblity is a false lean code, the o2 sensors pick up and react with the amount of oxygen left in the combustion to produce a voltage. When a cylinder doesnt fully fire it detects a large amount of oxygen because the fuel just passes right through causing the computer to think that its running a higher a/f when its not. The pcm will then try to compensate by dumping raw fuel into an already rich engine and it also will do this to the other side when it doesn't even need fuel. The PCM isn't perfect and will flaw when the you don't have the engine set up correctly.

the reason you dont see any other cells is b/c it sounds like you are in open loop which is where the PCM reads no feedback from the O2 sensors... same as when you are on start up. unless you the car was tuned extensively on a dyno with a wideband O2 then the car is likely running pretty rich or lean(hopefully not!).

Originally posted by turbo_Z
the reason you dont see any other cells is b/c it sounds like you are in open loop which is where the PCM reads no feedback from the O2 sensors... same as when you are on start up. unless you the car was tuned extensively on a dyno with a wideband O2 then the car is likely running pretty rich or lean(hopefully not!).

The car was recently dynotuned with wideband O2 and it runs better than it did before, but it still gets <10mpg, so I doubt it's running lean.
The scanmaster is reading all sorts of O2 voltages because the readouts bounce all over the place constantly. At startup, they read 4xx until they're warmed up, IIRC.
Which brings me to another question, There are 3 O2 readouts on the Scanmaster LT-1. There's a left and a right and there's an initial reading in the Scanmaster's start up display along with a retard output. Where does this third reading come from? Are there 3 O2 sensors?

Originally posted by JPSartre12
The car was recently dynotuned with wideband O2 and it runs better than it did before, but it still gets <10mpg, so I doubt it's running lean.
The scanmaster is reading all sorts of O2 voltages because the readouts bounce all over the place constantly. At startup, they read 4xx until they're warmed up, IIRC.
Which brings me to another question, There are 3 O2 readouts on the Scanmaster LT-1. There's a left and a right and there's an initial reading in the Scanmaster's start up display along with a retard output. Where does this third reading come from? Are there 3 O2 sensors?

the voltage will still fluctuate and the sensor will still relay information to the PCM.. it just gets ignored. the 3rd reading is actually just the reading from the pass side O2 sensor so you are looking at twice basically.

Originally posted by turbo_Z
the voltage will still fluctuate and the sensor will still relay information to the PCM.. it just gets ignored. the 3rd reading is actually just the reading from the pass side O2 sensor so you are looking at twice basically.

How do I know if my O2's are bad then?

Originally posted by JPSartre12
How do I know if my O2's are bad then?

a healthy sensor will fluctuate from 0-999 mV when its up to opporating temps and a dying sensor will either be frozen or maybe only range from 200-500 mV. this is when they are hot so after 5 min of driving is when you should observe them. doesnt really matter though in your case b/c your car isnt even using O2 sensors.

Originally posted by turbo_Z
a healthy sensor will fluctuate from 0-999 mV when its up to opporating temps and a dying sensor will either be frozen or maybe only range from 200-500 mV. this is when they are hot so after 5 min of driving is when you should observe them. doesnt really matter though in your case b/c your car isnt even using O2 sensors.

How do I know if it's running in open loop?
Is cell 18 an open loop cell?

Originally posted by JPSartre12
How do I know if it's running in open loop?
Is cell 18 an open loop cell?

yes 16 is idle and 18 is off idle.

Originally posted by turbo_Z
yes 16 is idle and 18 is off idle.

OK, now that I know that my car is always in a closed loop cell, how do I get it out of them? I know that there must be a reason, like a faulty sensor, etc., that got me to this point. Does anyone have a troubleshooting flowchart that tells you what to check in a systematic manner?
If it helps, my scanmaster reads 0 in both EGR and CCP, so I'm guessing that both have been disabled. Could this be why it's always in closed loop?

Thanks:think: