8.1 Gi-J SPN 29 FMI 4, 697, 698, 699 FMI 5, SPN 713 FMI 4

I have a 8.1 Gi-J non-catalyst with serial # A140969 in a 2011 Cobalt. I have the following fault codes and need help as I don't have access to any EGC manuals. I ordered EGC Diagnostic Manual 7749393 but don’t know when it will be here and no local dealers have it.

Codes were pulled using a Rinda TechMate Pro. I ordered the Rinda Diacom laptop software and cable, which will be here tomorrow.

SPN 29 FMI 4
SPN 697 FMI 5
SPN 698 FMI 5
SPN 699 FMI 5
SPN 713 FMI 4

I can clean them and they all come back. The SPN 29/FMI 4 will clean and come back when I go back into neutral from an RPM range.

I’ve replaced the throttle lever assembly part # 21157475.

I have two new batteries.

Knock sensors are reading 0 volts at idle or any RPM.

I tested a known good PCM and the same fault codes are present.

At this point I’m stumped and would appreciate any help.

muc notes --- replaced TCP with new.
The only change was that one fault never return which was SPN 91 FMI 4.

The SPNs 697,698,699+713 will always be there if you have can bus gauges and I think you do because you're not complaining that no gauges work.

SPN 29/FMI 4 is DTC 2127 = TCP #2 voltage low
This fault will set if voltage is less than 0.090 volts at any operating
condition while the key is ON.

SPN 91/FMI 4 is DTC 2123 = TCP #1 voltage low
This fault will set if voltage is less than 0.2 volts at any operating
condition while the key is ON.

TCP stands for Throttle Control Position
It is the driver’s throttle request for this drive by wire system. The throttle cable from the helm connects to this sensor. As the driver moves the helm lever, the throttle cable moves the TCP. The ECM sees the TCP input, looks at other inputs and determines where it wants the throttle blade set.
I'm surprised that when you replaced this sensor it would fix one DTC but not the other, because they are both in the same housing along with the IVS (idle validation switch). Another thing that surprises me is that you state that the DTC doesn't set until you return the throttle to idle. This DTC should set within 0.5 seconds and doesn't seem to be setting until you pull the throttle back.

This is why I recommend that you check the part that you replaced to make sure you got a good one. This sensor was one of the most often failed parts we saw back then and Volvo redesigned this part due to too many failures. It was a composite housing and the redesigned part has a metal housing. Maybe you got old stock? The good news is that with a scan tool this is a fairly simple test. This is one of the areas that Diacom is soo much better than TechMate. You can see all 14 parameters on one screen instead of having to keep repeating the test 7 times and you can also graph the results making interpretation soo much easier.

What you're looking for is for TCP #1 and #2 volts to go up with each other as you move the throttle handle. TCP #1 should increase at about twice the rate of TCP #2. At no time should TCP #2 drop below 0.09 volts and TCP #1 shouldn't drop below 0.2 volts (see how the low voltage threshold for TCP #2 is about half of TCP #1?) you want to see these voltages increase very smoothly as you advance the throttle from idle to W.O.T. They should raise to about 4.6 volts for TCP #1 and 2.3 volts for TCP #2. While you're doing this test also check the IVS for proper timing. This is 5 volts at idle and quick drop to around 1.7 volts as you advance the throttle.

These tests can be done KOEO (Key On Engine Off) there are 2 places in the scan tool -- the throttle monitor section and the drive by wire test. I can't remember what one I used in TechMate (I hated that tool!) but I seem to remember one was easier. Maybe try both?

Edit: I always forget to add this. Before doing any of these tests. If you haven't already done this. The first step is the visual inspection! Disconnect the batteries, unplug the shore power. Unplug the wiring connectors at the TCP, throttle body and ECM. Use a magnifier and good light and take a very good look at all 6 sides. NO corrosion NO damage

Let us know what you find.

At 56 seconds you’ll see TCP # 2 drop to .08 volts when it returns to idle.

The new TCP is the updated version.

I'm sorry but trying to watch that screen gives me a headache.
Can you post the Diacom .rec files?

Like the actual file or? Not sure the best way. I can email you the file?

Here try this. Should be better quality. If you open the video in YouTube and watch it full screen.

It happens at the 1 minute mark. This is with the engine running.

Here is one file with the engine running.

Here is another one with key on, engine off. You'll see TCP # 2 voltage starts at .08 volts. This is because the fault code is active. If I clear the fault code, it will always be at .09 volts. Once the fault code is active, it always starts at .08 volts.

This is one of the engine parameters at idle with some part throttle pulls just to see the engine data.

Question, should the ignition switch voltage be the same as battery voltage? It's a little lower.

Here is another longer one showing engine data.

Just to test I installed a brand new Arco alternator that I had on a new engine build yesterday to see if it would fix the issue but nothing changed.

Yes, those are the files I wanted.

"Question, should the ignition switch voltage be the same as battery voltage? It's a little lower."
That's very common to see be a bit lower. The battery feed goes to pins 60 + 79 and battery voltage is an average of those two. ignition feed goes all the up to the key switch and comes back to pin 45 where it provides the wake up power to the ECM. So a lot longer wire and consequentially more voltage drop.

I had very little time to look at these today, but thought I saw a couple of things that look off. When I went to look again tonight I found that I seem to have lost the graph function. Time permitting I will try again tomorrow.

Did you do a very good visual inspection? What I've seen so far is pointing to poor connections.