This may sound like a strange question but wondering if anyone has any experience or has seen any operating issues with a running voltage of 12.2? The car always starts and the battery seems strong but charging never seems to go over 12.4 volts. Wondering if this would effect the ECM with any drivability issues before I continue any tuning.
I don't know what that ecm part number means, perhaps you transposed some numbers . There are many corrections for voltage, here are a few examples in a GM 'puter and there are many more. Other than this, fix your alternator, everything will be happier running close to 14v
Code:Base Spark Dwell Time (msec) Vs. RPM Vs. Voltage RPM Volts 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 0 22.80 22.80 22.80 22.80 22.80 22.80 22.80 19.16 13.40 9.27 7.34 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 400 22.80 22.80 22.80 22.80 22.80 22.80 22.80 19.16 13.40 9.27 7.34 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 800 22.51 22.51 22.51 22.51 22.51 22.51 22.51 18.89 13.40 9.27 7.34 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 1200 21.05 21.05 21.05 21.05 21.05 21.05 21.05 17.45 12.96 9.27 7.34 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 1600 18.31 18.31 18.31 18.31 18.31 18.31 18.31 14.86 11.98 9.26 7.34 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 2000 16.08 16.08 16.08 16.08 16.08 16.08 16.08 13.18 11.12 9.15 7.34 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 2400 14.54 14.54 14.54 14.54 14.54 14.54 14.54 11.99 10.24 8.78 7.34 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 2800 13.34 13.34 13.34 13.34 13.34 13.34 13.34 11.06 9.48 8.31 7.20 6.14 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3200 12.39 12.39 12.39 12.39 12.39 12.39 12.39 10.32 8.88 7.81 6.95 6.09 5.30 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3600 11.63 11.63 11.63 11.63 11.63 11.63 11.63 9.70 8.36 7.37 6.61 5.96 5.29 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 4000 11.02 11.02 11.02 11.02 11.02 11.02 11.02 9.21 7.96 7.04 6.31 5.71 5.20 4.67 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 4400 10.49 10.49 10.49 10.49 10.49 10.49 10.49 8.78 7.60 6.72 6.05 5.49 5.03 4.60 4.16 3.78 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 3.45 4800 10.02 10.02 10.02 10.02 10.02 10.02 10.02 8.42 7.29 6.44 5.81 5.29 4.85 4.48 4.12 3.75 3.42 3.42 3.42 3.42 3.42 3.42 3.42 3.42 3.42 3.42 3.42 5200 9.60 9.60 9.60 9.60 9.60 9.60 9.60 8.09 7.01 6.20 5.58 5.09 4.68 4.33 4.01 3.68 3.36 3.36 3.36 3.36 3.36 3.36 3.36 3.36 3.36 3.36 3.36 5600 9.26 9.26 9.26 9.26 9.26 9.26 9.26 7.80 6.76 6.00 5.40 4.91 4.51 4.18 3.88 3.56 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 6000 8.94 8.94 8.94 8.94 8.94 8.94 8.94 7.54 6.55 5.81 5.23 4.76 4.38 4.06 3.75 3.43 3.15 3.15 3.15 3.15 3.15 3.15 3.15 3.15 3.15 3.15 3.15 6400 8.65 8.65 8.65 8.65 8.65 8.65 8.65 7.29 6.35 5.64 5.08 4.62 4.26 3.95 3.65 3.33 3.05 3.05 3.05 3.05 3.05 3.05 3.05 3.05 3.05 3.05 3.05 6800 8.39 8.39 8.39 8.39 8.39 8.39 8.39 7.08 6.17 5.47 4.94 4.50 4.13 3.84 3.54 3.24 2.96 2.96 2.96 2.96 2.96 2.96 2.96 2.96 2.96 2.96 2.96 7200 8.15 8.15 8.15 8.15 8.15 8.15 8.15 6.88 5.99 5.32 4.80 4.38 4.03 3.74 3.45 3.15 2.89 2.89 2.89 2.89 2.89 2.89 2.89 2.89 2.89 2.89 2.89 7600 7.92 7.92 7.92 7.92 7.92 7.92 7.92 6.70 5.84 5.18 4.68 4.27 3.94 3.65 3.36 3.07 2.81 2.81 2.81 2.81 2.81 2.81 2.81 2.81 2.81 2.81 2.81 8000 7.74 7.74 7.74 7.74 7.74 7.74 7.74 6.53 5.70 5.06 4.57 4.16 3.83 3.56 3.28 3.01 2.75 2.75 2.75 2.75 2.75 2.75 2.75 2.75 2.75 2.75 2.75Code:Injector Offset (msec) Vs Battery Voltage Vs MAP Volts Kpa 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 4.5 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 5.0 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 5.5 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 5.67 6.0 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 5.33 6.5 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 4.32 7.0 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 3.30 7.5 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 2.78 8.0 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 2.25 8.5 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 2.02 9.0 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 1.79 9.5 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 1.60 10.0 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 10.5 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 1.29 11.0 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19 11.5 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 1.08 12.0 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 0.97 12.5 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 0.91 13.0 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 13.5 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79 14.0 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 14.5 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 15.0 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 15.5 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 0.59 16.0 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 16.5 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 0.52 17.0 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 17.5 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 18.0 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43
-Carl
Oops, sorry. I meant 1227747. Seems I'm getting everything backwards theses days. I presume the chart you posted shows what will change with battery voltage or how the ECM corrects for it?
Last edited by JF in MI; 09-02-2021 at 07:50 PM. Reason: addition
Before doing any tuning, fix your charging issue, or the way you're reading the voltage.
12.4 isn't even maintaining battery voltage, you need at least one volt above nominal battery voltage to be considered charging, in a 12V system, this is 13.6V, and prefered to be nearer 14.4 volts, so that you can be charging the battery AND have enough for running everything else.
I don't know what you're using for reference for the voltage reading you are seeing. If it's the dash gauge, perhaps it's reading incorrectly, or if you are using a DMM, perhaps the battery in it is low, or not a good reference ground, etc.
ALWAYS, ALWAYS, ALWAYS, ALWAYS fix any and all known issues, mechanical or electrical before trying to tune a vehicle. You'll be chasing your tail if you don't.
The man who says something is impossible, is usually interrupted by the man doing it.
Perhaps I should have rephrased my question. The alternator problem was fixed. What I'm wondering is does this mean that any of the tuning I had done before the fix (with lower voltage) is now useless or what may change, in the previous tuning, now that I have proper running voltage.
No, the permanent portion of the tune is preserved in a form of memory that is non-volatile. That is, it is unaffected by voltage. However, there is a small portion of memory area that DOES need a small permanent voltage applied. This area retains the "learned" parameters for what the engine needs for a stable idle RPM, easiest starting and the drivers transmission shifting habits.
You will still have the main, largest portion of the tune if the retained learned parameters are lost but it will take a few minutes or maybe a drive cycle or two to regain overall system performance.
Rick
1970 Chevy El Camino, LM7 Engine, 4L60E - Two 896 and two 0411 PCM's
Thanks. I was concerned that it may have caused the sensors to read different or something crazy like that.
you'll find most important sensors work by measuring against a 'reference voltage' of usually 5 volts or so which is regulated down from the battery input voltage.
whether you're running at 11v or 14v input, that 5v reference pretty much stays at 5 volts. the ecm is totally designed to run at low voltage.
That's what I thought but wanted to confirm it from someone more knowledgeable than me.
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