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LH 2.4 ECU Pin 30 is a MYSTERY to me.

dbarton

Dejected by Volvo Corp.
Joined
Nov 17, 2002
Location
Prosper, TX
I have questions about PIN 30. I'm finding conflicting information in all of the diagram info I can find.

Pin 30 description in most sources says stuff like this:
Park/Neutral position (PNP) switch (automatic transmission).
Information on gear selector position. Used to keep idling speed constant when gear is selected.
P N position: U low (no signal).
D 1 2 3 R: bat (12v signal).
Manual: U low (no signal).

First pic below from: https://ipdown.net/jetronic.info/tiki-index.php?page=LH2.4%20Pinouts%20and%20Diagrams

I understand the concept that LH 2.4 can receive a signal from the auto trans gear selector and adjust the idle when "in-gear." The mystery I have is that I find NO DIAGRAM ANYWHERE which supports that any LH 2.4 Volvo actually used this function.

The only diagrams I find suggest that Volvos using LH 2.4 only sent voltage to Pin 30 when the starter motor is engaged.

Nothing in any P-shift lock diagram points to the answer either.

So does anyone know if the above gear selector idle-increase function actually existed in a Volvo, and maybe Volvo forgot to put it in a diagram, or was this function not used by Volvo?

Thanks, Dave
 

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Further, it appears to me the input signal symbol used in the above photo (arrow pointing to left) is correct, but in SOME diagrams the below output ground signal symbol is used. That seems completely wrong to me.

Dave
 

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Agreed the symbol showing 30 to be an output is just one more example of the high error rate in the interior greenbook wdm pages. On LH2.4 ECUs used with 240 Volvo, it is definitely an input to pin 14 of the hybrid, not an output.

The pin function tables I've seen for years (from saabnet and others) all describe that pin 30 as one to sense the transmission selector in LH2.4.1 and LH2.4.2. Like you, I've only seen it used to sense cranking, and I'll bet, because it is pulled up to +5V and not battery, it was never intended by Bosch to look at the starter solenoid.

Someone who was diagnosing a no- or intermittent-crank recently mentioned having a strange reading on the solenoid wire with the starter disconnected, and one of us suggested the ECU as the source of it. Now, tracing this to +5, the reading is in my mind explained.
 
Like you, I've only seen it used to sense cranking, and I'll bet, because it is pulled up to +5V and not battery, it was never intended by Bosch to look at the starter solenoid.

It makes me think that maybe this pin should be ignored for people doing their own installations, unless there's a benefit to smoother starting where the idle speed is momentarily increased (maybe idle valve opens more?) just during cranking.
Dave
 
I'm WFH 40+ hours a week, but later this week I'll try to see if the P/N pin actually changes the idle.

With a manual transmission, or an automatic in P/N, the starter solenoid coil acts as a very strong pulldown resistor. The ECU will sense ~0 volts normally, and ~12volts when the starter is engaged.

With an automatic that's in gear (not P/N) the starter wire is disconnected and there's a weak pullup resistor in the ECU that sets the voltage on pin 30. IDK if it's a pullup to 5volt regulated, 10volt regulated, or Vbatt.
 
I'm WFH 40+ hours a week, but later this week I'll try to see if the P/N pin actually changes the idle.

With a manual transmission, or an automatic in P/N, the starter solenoid coil acts as a very strong pulldown resistor. The ECU will sense ~0 volts normally, and ~12volts when the starter is engaged.

With an automatic that's in gear (not P/N) the starter wire is disconnected and there's a weak pullup resistor in the ECU that sets the voltage on pin 30. IDK if it's a pullup to 5volt regulated, 10volt regulated, or Vbatt.

You're right. I'd thought it cared for the double squirts I'd read about happening during cranking, but it makes more sense it changes fuel between park and drive, like the Saab pin charts say. The input is not logic for the mpu, but analog on the hybrid.

lh24_30.jpg
 
With an automatic that's in gear (not P/N) the starter wire is disconnected and there's a weak pullup resistor in the ECU that sets the voltage on pin 30. IDK if it's a pullup to 5volt regulated, 10volt regulated, or Vbatt.

Please correct me if I'm not getting something.
If the starter (term 50) is connected to pin 30 or not, what difference would it make as long as no one turns the key to start? Connected or not connected. Is there some other circuit I'm not seeing that causes a change at pin 30 if term 50 is severed from the key switch?
Dave
 
The ignition switch start wire goes to the ECU, then through the P/N interlock switch, then to the starter solenoid. When in P/N, the solenoid coil is a low resistance path to ground -- pin 30 will see ~ground unless cranking, which will give ~12v on pin 30. When in drive, the interlock switch opens, leaving the weak ECU internal pullup resistor to +12v on ECU-30. So pin 30 goes high during starting, and when an automatic is shifted out of P/N.
 
The ignition switch start wire goes to the ECU, then through the P/N interlock switch, then to the starter solenoid. When in P/N, the solenoid coil is a low resistance path to ground -- pin 30 will see ~ground unless cranking, which will give ~12v on pin 30. When in drive, the interlock switch opens, leaving the weak ECU internal pullup resistor to +12v on ECU-30. So pin 30 goes high during starting, and when an automatic is shifted out of P/N.

Thanks. Starting to make some sense now. My brain is wired for hot/cold, black/white, and voltage/ground, so things like low resistance paths are more difficult for me.
Dave
 
The ignition switch start wire goes to the ECU, then through the P/N interlock switch, then to the starter solenoid. When in P/N, the solenoid coil is a low resistance path to ground -- pin 30 will see ~ground unless cranking, which will give ~12v on pin 30. When in drive, the interlock switch opens, leaving the weak ECU internal pullup resistor to +12v on ECU-30. So pin 30 goes high during starting, and when an automatic is shifted out of P/N.

Right again, Bob. It seems I lost count on the ECU pins. Not pulled to +5. Pulled to +12 by a 1KΩ resistor. Revised the drawing above.

Simple test: Connect voltmeter to starter test terminal. Turn ignition key to KP-II. Set parking brake. Move AW selector to R (or anything not P or N) and see the battery voltage appear on the voltmeter.
 
^^^ We need the followup test - with the wire connected to the starter test terminal, and the AW in R or D, touch the wire to ground while idling and see if you notice any change at all in the idle. If the ECU is adjusting idle speed, it should change (drop) when the wire is grounded because the ECU will falsely think the transmission has been shifted into P/N.

I traced ECU-30 to the hybrid-14, as a 0 to 12v signal, and then off the hybrid-24, as a 0 to 5v signal, to CPU-65 -- Port5.2. So, it does go to the ECU but I wasn't able to see it do anything to the IAC control signal on the benchtop.

I did see the LH injection switch from 2 squirts per rev during cranking to 1 squirt per rev when running. I think it's just based on rpm - below 500 rpm is 2 squirts/rev, once over ~520rpm, it goes to 1 squirt/rev and stays there until engine is turned off. I'll try to capture and post pics in the next few days. Arctic blast is predicted for Sunday (17deg overnight), so it will be a good day to stay in and tickle the oscilloscope knobs.
 
I now have the definitive answer. Yes, LH2.4 ECU pin 30 does increase the idle when shifting from P/N into drive.

On my cold engine, with a '937 ECU and '148 EZK, the idle speed in Park after a couple minutes warmup hovers around the factory 775 rpm. When I disconnect the starter switch wire from the solenoid, while still idling, the idle speed goes up to ~885 rpm. Disconnecting the wire is the equivalent of opening the P/N switch, but while the transmission is still in Park.

Happy Easter,
Bob
 
As promised, here are a couple benchtop oscilloscope pictures showing a '951 LH2.4 box switching from "cranking" with 2 long squirts per rev, to "running" with 1 shorter squirt per rev. "Cranking" is up to 515rpm, and it switches to "running" as soon as it gets to 520rpm. [An older '563 box switched at a higher speed of ~580rpm.]

The scope traces from top to bottom are:
chan 6 = wheel generator reference, one pulse per every 2 revs
chan 1 = RPM signal (EZK to ECU), one pulse per cyl
chan 2 = Idle Air Valve
chan 3 = Ignition (high ~5volts = charge coil)
chan 5 = Injectors (low ~0volts = energize injector)

Here's the '951 box "cranking" at 515rpm. The scope trace shows ~3 1/2 revs, with 2 squirts and 2 sparks per rev. While cranking, the injector pulse width is ~6ms per squirt.
LH2-4-951-Cranking-515rpm.png


And here's the '951 box "running" at 520rpm. The scope trace shows ~3 1/2 revs, with 1 squirt and 2 sparks per rev. Even though there are half the squirts, the injector pulse width has dropped to ~4.5ms per squirt when "running". If we assume a 1ms dead time, cranking is 20ms fuel per cycle versus only 7ms per cycle running.
LH2-4-951-Cranking-520rpm.png


-Bob
 
I appreciate the help.

I've been working on new pin function diagrams for LH 2.0, 2.2 and 2.4. I use this kind of stuff often to help others with wiring issues and having some simple diagrams I can look at or send really comes in handy. I've found so many errors and inconsistencies in some I found from other sources, so I decided to make my own. Hopefully I have them right.

I've posted them in my page in case anyone can use em.
https://www.240turbo.com/volvoharnesses.html#pinfunctions
Dave
 
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