Ftech9

The Fluke 117 will work well, however if you don't need the "Auto-V/LoZ" and "Volt Alert" features you can get away with the Fluke 115.

I personally have the Fluke 289, it was extremely expensive, but the accuracy for low voltage/amperage measurements is amazing for engineering work.

- Joe

Tom Pultz

I ran some simple tests today:
Test 1 - Cold Engine w/Engine OFF, Ignition ON
Idle Position Throttle Switch (TS) Mode - Idle; barely move throttle, Mode changes to Full Load (should be Off Idle); back off throttle, Mode changes back to Idle. Repeat, repeat, repeat... same result.

Test 2 - Engine OFF, Switch Ignition OFF, then ON again
Idle Position TS Mode - Full Load (should be Idle); barely move throttle, Mode changes to Off Idle, back off throttle, Mode changes back to Full Load. Repeat, repeat, repeat... same result.

Test 3 - If I repeat Test 2 (switching the ignition OFF and ON) a few times I can get the same results as Test 1, but it seems the longer I keep the ignition ON while testing, eventually I can't get the mode to indicate Idle with the throttle closed, indicating something in the DME or KLR that changes after power is applied for a period of time.

Test 4 - Engine RUNNING
Idle Position TS Mode - Full Load (should be Idle) barely move throttle, Mode changes to Off Idle, back off throttle, Mode changes back to Full Load. Repeat, repeat, repeat... same result. These are the operating modes I always get with the engine running. I can never get Idle mode with the throttle closed.

One item to note: the ICV % Open started out around 70% and very gradually increased to around 85% open during the period the engine was running.

Test 5 - Engine OFF, KLR Disconnected, Ignition ON
Same results as Tests 2 or 4.

I really don't know how to interpret these test results. On one hand the KLR might be at fault since it appears to be sending a Full Load signal with the throttle in the idle position. But on the other hand, if the KLR is disconnected the OBD+ software (SW) still thinks the mode is Full Load in the idle position, which doesn't physically seem possible unless the SW latches the previous value when the engine was running.

I ordered a new DVM and will run through the various troubleshooting tests in the Turbo WSM when I receive it. To me it currently seems like the "TPS" may be functioning correctly since there are tests when the mode is Idle with the throttle closed, and other times the mode is Off Idle with the throttle advanced, both of which would indicate normal operation. However, I can't get them to display in that order, which points to OBD+ software and/or KLR (most likely problem?) issues.

If anyone else has performed any of these tests, please post your results. Thanks.

Tom Pultz

I think this is the only meaningful test I ran since the engine must be running for the KLR to work correctly. As Joe stated earlier in this thread, for the DME to enter Full Load it must sense BOTH an Off Idle condition and WOT. The DME may be working correctly but the status values reported by the OBD+ are FALSE. The OBD+ doesn't report the separate status of the microswitch inside the throttle switch (but OBD+ really should report this status separately as a double-check), it just reports what it thinks the throttle position is: Idle, Off Idle, or Full Load. If the SW thinks the throttle status is Full Load at idle but the engine idles fine (like mine), just at too high rpm, it seems that the voltage the OBD+ is sensing from the KLR to determine when to display Full Load may need to be adjusted to avoid what looks like false positives, since it is known (from others that have done tests) that the KLR does spit out spurious lower-level voltages (which is why I get the mixed results with the engine OFF) that seem to be getting incorrectly interpreted by the OBD+ SW as a "Full Load" signal, when in fact, it is not.

If my combo throttle switch isn't adjusted properly or has a faulty microswitch what I should see is Off Idle with the throttle closed, and Off Idle with the throttle open with the engine running. Based on how the engine runs, this appears to be the true status of the system. Before I change the throttle switch, I'll run tests to verify the actual condition, but that's a week or so out while I wait for my new DVM to arrive.

This whole discussion points out that Ftech9 DME w/OBD+ owners really, really need documentation of all these OBD+ parameters and how to interpret them, otherwise we are just spinning our wheels trying to solve issues.

Ftech9

Hi Tom,

To help with diagnosis, I just added a special version of the FocusOBD (v0.25.278) software to the website. This build of the software displays the raw voltage measurement for the throttle switch as seen by the DME's ADC (Analog to Digital Converter). When this version loads, you will be prompted to update the OBD+ module’s firmware. Just click "ok" and it will automatically update in less than 30 seconds.

For this to be useful, it is important to understand that the DME does not actually read the two digital inputs for idle and full-throttle directly. These two inputs are process by a resistor network and combined into a three-state voltage level. That voltage level is then fed to the DME’s ADC and is read out like any other analog sensor. Below are the approximate voltage levels that trigger each mode:

Idel ~3V

Off Idel ~5V

Full Load ~3.8V

I would start by disconnecting the KLR and Throttle Switch then verify the Throttle Switch voltage is close to 5 volts. The next test would be to short terminals 4 and 6 on the throttle switch connector with a wire to simulate closed idle contacts. This is expected to drop the throttle switch voltage to about 3 Volts. If one or both of these tests fail, this would indicate an issue with the DME. If this case, I will send you a replacement to try out with return shipping for the original.

Also, full load cannot be tested unless the engine is running, I verified this on my 1986 944 Turbo. The factory service manual suggests disconnecting two injectors to prevent the engine from over revving while pressing the throttle all the way. Personally, I just pressed the throttle momentarily to trigger full load without the RPM coming up too high.

If you are willing, download FocusOBD v0.25.278 from the website and let me know the results.

-Joe

Tom Pultz

I installed the Alpha version and performed a few tests with the engine OFF:

Test #1: Everything hooked up as usual. Turn ignition ON, Mode = Idle, V = ~ 2.70; move the throttle - Mode = Full Load, V= 3.78-3.80.
Test #2: Ignition OFF, then ON again, Mode = Full Load, V = ~3.80; move the throttle - Mode = Off Idle, V = 4.96.
Test #3A: Disconnected both KLR and Throttle Switch connectors. Ignition ON, Mode = Off Idle, V = 4.96.

I'll perform the connector shorting test when I find a suitable small gauge wire or get some appropriate test leads for the tiny contacts, but so far Test #3A resulted in the expected voltage, so that's a positive (no pun intended )

So, at this point it does look like the microswitch in the TPS may be at fault, but I am still confused, and frankly annoyed, why OBD+ displays incorrect Modes with the engine off or on. This certainly adds confusion to troubleshooting and to me seems flat-out incorrect. After I perform the connector short test, I'll hook everything back up and run the engine and see what TPS voltage is displayed.

BTW, any hints on what combination of "wrenches, screw drivers, etc." works best to get that lower Phillips screw unscrewed on the TPS? I know once that's removed some owners replace those screws with small Allen-Head.

Thanks for all your help, Joe. The DME looks OK at this point.

Tom Pultz

I performed another test today.
Test #3B: disconnected KLR and Throttle Switch, terminals 4 and 6 on Throttle Switch jumped with a paper clip: Ignition ON, Mode = Idle, V = 2.95.

So, I'm getting the expected modes and voltages for the two test conditions Joe requested. However, none of these results explain why I'm getting incorrect modes shown with everything connected and the engine running. Based on the results of tests #3A and #3B, if my Throttle Switch has a bad microswitch I should be seeing Off Idle with the throttle closed or open less than WOT, but I don't see those modes; I see Full Load mode displayed with the throttle closed, which is exactly what the NBO2 sensor thinks is the case since the voltage doesn't oscillate until you barely crack the throttle and the mode changes to Off Idle.

Question for Joe: Do the modes displayed drive the way the system operates or are the modes derived from how the system is operating, and are "for information only" based on what the software thinks is happening? I don't see how the DME can actually be operating in Full Load mode at idle, but that's what the NBO2 sensor thinks is happening since its output is ignored at WOT. However, if the DME was actually operating with the WOT maps at idle I wouldn't think my idle quality would be as good as it is, or the engine may not even idle or run very well at all.

Ftech9

Hi Tom,

There is a possible failure mode where the idle contacts could emulate a "full load" state. Note that "off Idel" is the largest voltage of the three states. This means to transition from "idle" to "off Idle" the voltage must swing past "full load" at 3.8 volts to reach "off idle" at 5 volts. It is normal to see an occasional glitch of "full throttle" in the FocusOBD software when transitioning from "idle" to "off idle”, especially noticeable when graphing. Both my 944 Turbo and 944 NA do this.

What may be going on in your case is that, when the idle contacts are closed, the resistance between the contacts is higher than it should be, possibly due to corrosion or oxidation. If the resistance was just enough to put the “idle” voltage closer to "full load" than to "idle," the OBD+ module would interpret this as "full load," most likely the DME program would as well. Unfortunately, I do not know the exact thresholds the DME uses to trigger each of these modes, that is arbitrarily set in the DME program. It would take someone who knows the DME program inside and out to determine the exact values (and schema such as hysteresis) from the hex code. However, in theory, I could likely find this out through experimentation by connecting a variable resistor to the idle switch input and adjusting it until the engine changes behavior when transitioning between the three states. Another thing I could potentially do is calculate the "idle switch" contact resistance and issue a warning before it reaches a failure point. I will note these features in in the OBD+ firmware project backlog for a future update.

- Joe

Tom Pultz

Sorry Joe, I composed this reply before I saw that you had replied.

OK, I ran another test with the engine running (KLR reconnected of course); I left the throttle switch disconnected with the terminals 4 & 6 jumped to simulate the idle condition. When the engine was cold it ran horribly with the idle fluctuating from barely running to something in the 8xx rpm range. During this time, the throttle switch voltage would swing back and forth between 1.9 and 2.95 V. The mode displayed was Idle. After the engine warmed up the idle speed was more stable, in the 8xx rpm range, the throttle switch voltage was 1.9 V, and did not cycle up and down. Interestingly, the ICV % Open was 115.5, which doesn't seem to make sense, but I don't really know the valid range for the ICV.

Not sure what to make of this test as the results weren't what I had expected. However, I suspect the engine doesn't like to run without a signal from the throttle switch potentiometer. Looks like it's time to replace the throttle switch.

Tom Pultz

Ah, that makes sense! Is this a "Eureka moment?" This scenario could explain why the OBD+ can show the throttle switch in Idle mode the first time the ignition is turned ON with the engine OFF, and then when the ignition is turned OFF and back ON again, the mode displayed is Full Load, etc.

Guess I don't need that multimeter I ordered... just kidding. I'll run through all the ignition tests before I change the throttle switch. The MM is to arrive next Tuesday.

Have a great weekend.

Ftech9

Hi Tom,

The DME and the KLR are virtually independent systems, except for the KLRs ability to pull back the ignition timing to control engine knock/detonation. Can you run the above test again with the KLR disconnected and the Sport DME's Ignition Mode switch set to "NA" mode? This takes the KLR completely out of the equitation allowing the DME to operate without its potential interference. I would expect the engine to start and idle normally in this configuration.

A WORD OF CAUTION
Make extremely sure you set the Sport DME’s ignition mode back to “Turbo” mode when you reconnect the KLR. Running a 944 Turbo in “NA” ignition mode disables the KLRs Knock control and very well could result in engine damage when boost pressure is applied. This is not an issue with the KLR disconnected because there will be no significant boost pressure.

Also, could you email me a data log while you are doing this? Simply check all the checkboxes in the Data Grid Tab (right side of screen) then press the “Record” button (bottom right side of screen). When finished, press the "Stop" button next to the "Record" button. Pressing the “Folder” button will open the folder where the log file is stored.

-Joe

Tom Pultz

Joe, I'll run this test and get you the data log, which probably won't be until Sunday as we are going to be busy all day tomorrow.

How long would you like me to record the data? And this may be a dumb question, but if the DME is set to NA, why does the KLR need to be physically disconnected? I tried doing that in Turbo mode and the engine wouldn't start.

Another test I can run that I haven't done since you added the ability to see the throttle switch voltage is to hook everything up again with the suspected faulty throttle switch, and run the engine and see what voltage corresponds to Full Load mode at idle. This may provide an additional clue why the DME is entering Full Load at idle.

BTW, I took a look back through this thread and users have apparently lost the ability to display additional parameters such as voltages corresponding to sensor outputs such as Intake Air Temperature and Coolant Temperature, and at one time you had a beta feature to set the ICV without disconnecting it or bridging the terminals on the test port. Did that procedure not work out as planned?

Have a nice weekend.

Ftech9

Hi Tom,

For the data logging, please start the recording before switching the ignition on, then stop after the test is complete.

The reason the 944 Turbo will not run without the KLR connected is because the Turbo DME does not control its own ignition driver circuit. The Turbo DME exports the ignition signal to the KLR. The KLR regenerates this signal then exports it back to DME on pin 32, which is the input for the ignition driver. The reason for this is so the KLR can modify the ignition signal to retard the ignition advance when it detects engine knock/detonation. When you change the Sport DME’s Ignition mode to “NA”, this loops back the ignition signal internally allowing the Sport DME to directly control the ignition driver. This is a handy feature to have in no-start situations. If the engine starts up in "NA" ignition mode, then you have a bad KLR. If this is the case, just disconnect the KLR and drive home in a no-boost "limp mode".

You can calibrate the engine base idle using the FocusOBD software as an alternative to the factory method of bridging terminals B and C on the test socket. In ether the factory method or this alternative, the engine must be thoroughly warmed up and the oxygen sensor unplugged. In the factory method, bridging the test socket commands the DME to hold the ICV open at a specific position. You would then adjust the idle to 840 RPM IIRC. In the alternative method using the FocusOBD software, the procedure is reversed. You would simply adjust the idle screw while observing the ICV percentage. In the Data Grid Tab, when you see the ICV percentage turn green (bright green if you are dead on), then the base idle is properly calibrated. I do not recall the exact percentage, but I believe it is around 85%. You can bridge the Test Socket terminal and see the ICV jump to the exact target percentage.

A bonus of doing the base idle adjustment using the FocusOBD software is you are also verifying if the ICV valve is function correctly. If the ICV is doing its job, the idle will stay at a fixed RPM until the ICV reaches its upper or lower limit. You will actually see, in real time, the ICV percentage change as you adjust the idle screw. The ICV open percentage is expected to decrease as the idle screw allows more air to bypass the throttle body. Conversely, as the idle screw restricts air bypassing the throttle body, the ICV percentage will increase. In both cases, the engine RPM should hold steady until you hit the ICV mechanical limits.

- Joe

Tom Pultz

That's what I'm asking, when is the test complete, right after it starts and idles OK, or continue recording until the engine warms up?
The OBD+ version you posted in October 2021 also displayed the ICV status in ms, which for the NA was ~ 3.52 and for the turbo, 3.57. The data you showed for the NA had the ICV open 85.8% and both values were green.

Please comment on the last test I ran that idled so badly where the ICV % Open was 115.5, which is physically impossible.

Thanks. I'll be running this test and the other test I suggested on Sunday.

Tom

Ftech9

It would be better if the data log continues until the engine warms up, at least until the DME enters closed-loop mode.

For the ICV percentage issue, what version(s) of the FocusOBD software did you observe it displaying 115.5? Does this happen every time, sometimes or just the one time?

-Joe

Tom Pultz

It was the Alpha 278 version and I only saw it on the last test with the bad idle.