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Old 09-23-2022, 10:24 AM   #26
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Join Date: Jul 2016
Location: MA/NH

this is what I have in my notes for the hybrid pinout. Remember this is for 572 lh3.1 and might be slightly different than lh2.4 or 9xx ecu. But the pcb of lh31 and 5xx lh24 are the exact same minus a few components. also don't assume anything is actually correct. you can kinda see one side of the chip is to signals external to the box and the other is signals to the internal circuitry/mcu.
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pin	label				pin
1	maf/volt comp?			mcu an6
2	cel out mcu			mcu p4.6	(also 30047 pin 13)
3	fuel pump relay control		(ext pin 20)
4					(ext pin 31)
5	tps related lh31		(ext pin 10)
6	RPM in from ezk			(ext pin 1)
7	ac switch			(ext pin 15)
8	obd? 				mcu p3.1
9	power(probably 12v maybe 5)
10	gnd (power ground?)
11	O2 input			(ext pin 24)
12	5v power rail
13	gnd 				(ext pin 5)
14	auto pnp			(ext pin 30)
15	WOT switch in			(ext pin 3)
16	knock enrich input		(ext pin 28)
17	iac in?				(ext pin 33)
18	ac clutch			(ext pin 14)
19	lh31 tps pot related?
20	gnd
21					mcu p5.0 
22	iac in?				mcu p4.0
23					mcu p5.5 
24	output from hybrid pin14 to	mcu p5.2
25					mcu p5.6
26					mcu p5.1
27	lambda rich/lean		mcu p1.7
28	lambda rich/lean		mcu p1.6
29	ezk rpm out to cpu		mcu p1.0
30	obd pin in/out			(ext pin 12)
31	watchdog related?		mcu p4.1
32	iac out to transistors
33	iac out				mcu p1.2
34	no connection
35	5v power rail
36					mcu p5.3
37	mcu/sram reset pin
38	no connection
39	watchdog related		mcu p3.3
40	fuel relay?			mcu p4.4
and here is the 30047 chip while im at it:
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pin	label				pin
1	to mcu p5.4
2	in - maf burn off/lh31 idle 	mcu p4.5
3	out - maf burn off/lh31 idle	(ext pin 8)
4	out - load output to ezk	(ext pin 25) 	confirmed
5	in - load from mcu		mcu p1.1
6	gnd
7	in - speedo input		(ext pin 34)
8	out - speedo to mcu		mcu p1.4
9	in - shift indicator		mcu p4.7
10	out - shift indicator		(ext pin 26)	confirmed
11	gnd
12	out - CEL/MIL			(ext pin 22)
13	in - CEL/MIL mcu out		mcu p4.6 (also hybrid pin 2)
14	in - injector mcu out		mcu p1.3
15	out - to injector transistor	(ext pin 18)
16	12v power - from sys relay?
17	out - unused to t318 base to 	(ext pin 11)
18	in -				mcu p4.2
19	5v power
20	pulled loosely to gnd (220k ohm)
1991 244 LH3.1 M46 402k miles
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Old 09-23-2022, 11:24 PM   #27
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Join Date: Aug 2014
Location: Boulder CO

I looked at pin 1 of the LH2.4 composite and think that ipdown is correct, but with a typo:
Originally Posted by ipdown View Post
I can tell you the basics the hybrid does as far as I can remember:
3. Precision 4.96v regulator for the ADC reference
I measure 4.06v on pin 1 (non-calibrated meter), and it certainly seems like a precision voltage reference. It didn't budge when I adjusted the 12V supply up and down a couple volts, nor when I adjusted the 5V supply up to 5.8V, nor when I heated up the hybrid to ~170degF.

I have no idea why Bosch would feed this into the ADC and use it to rescale every MAF measurement in software. It doesn't make any sense. Standard designs either use a precision reference for the analog electronics and for the ADC Vref pin, or just use a well regulated 5.0V supply for everything.

I looked at the LH2.3 schematics and think that the hybrid is the same as, or very similar to, the LH2.4 hybrid. Slightly different signals may be fed through it. The Porsche FLAPPY reference is to a controllable helmholtz resonator on the 928 S4 intake, while Volvo LH2.4 has some VSS circuits instead.

Misc other comments:
- MAFadc0 = (MAFin – 2.40v) * 1.35 + 0.04v (and 0.04v for MAFin < 2.40v)
- the 30047 chip looks like a simple level translator, including both 5v to 12v and 12v to 5v buffers.
- The Best of Bob Pease
- Semiconductor Chip Logos

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Old 09-27-2022, 12:57 PM   #28
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I looked at a handful of lh2.4 bins in regards to this and it turns out they only do this maf logic I described on 5xx ecus. The maf logic on the 9xx ecus is simply airflow_result = maf_linearization_map[ 0xC3 ] .

The 9xx bins do still use this 0xC9 value from the hybrid pin 1 to ADC pin an6 as some sort of boolean logic (true if > 2.5volt / false if < 2.5volt) in a couple places around the code but doesn't look like anything major. Notably something to do with cold start cranking and load transient logic.
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Old 09-27-2022, 01:46 PM   #29
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On the contrary, I've also found this post from ipdown 10 years ago that says adc buffer 0xC9 is from a code plug - external pin 19, which I am pretty sure i've ruled out (atleast on 5xx ecus) but will check again once I get some spare time.
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Old 10-03-2022, 10:12 PM   #30
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I don't know if this will help at all, but here's my results from tracing the LH2.4 hybrid signals on the bench. YRMV.
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~9/30/22 LH2.4 bench test results

HYB = Thick Film Hybrid, 40-pin
ECU = LH ECU 35-pin connector
MCU = 80C535 Microcontroller, 68-pin PLCC pkg

Measured with Bosch 0280000937 ECU (B230FT non-egr and 12.0V bench supply

Pin	Notes                                To/From
---     ----------------------------------   --------------------------------------

HYB-9   +12V
HYB-12  +5V
HYB-31  +5V  (LH2.4 this may be a tied-off input instead of power pin)
HYB-35  +5V
HYB-1   4.06v voltage reference output       n/c

HYB-4   LH2.4                                n/c
 - LH2.4 stays at ~12v
HYB-5   LH2.4                                n/c
 - LH2.4 stays at ~5v
HYB-40  LH2.4                                MCU-6/P4.4
 - LH2.4 stays at ~0v

RPM, Reset and Fuel Pump Related
HYB-6   LH2.4 RPM input                      ECU-1
 - RPM input from EZK, 0.6v to 9.7v
HYB-29  LH2.4 ezk rpm out to cpu             MCU-36/P1.0
 - RPM output, 5v to 0v (inverting from HYB-6)
HYB-34 something to do with rpm              n/c
 - 4v at 0rpm, negative sawtooth at rising rpm edge, 4v down to 0.9v

HYB-37  LH2.4 mcu/sram reset pin             MCU-10/RESET

HYB-39  LH2.4 watchdog reset from software?  MCU-25/P3.4
 - goes to 5v for ~50ms after powerup, then changes to ~1kHz square wave
HYB-38  LH2.4 ???                            n/c
 - low level signal with ~1khz/1ms tiny noisy square wave
HYB-2   LH2.4 RPM OK status to MCU?          MCU-8/P4.6
 - goes from 0v to 4.9v ~100us after first rising EZK RPM edge, goes to 0v ~0.77sec after RPM stops
    (RPM from EZK stops high then goes low after ~0.73sec, HYB-2 goes low ~38ms later)

HYB-3   LH2.4 fuel pump relay output         ECU-20 (after T302 and CA3272 driver)
 - 10.2v 0rpm / 0.5v 800rpm

 fuel pump turns on ~100uS after first rising EZK RPM edge, or ~0us after first falling RPM edge to MCU
 fuel pump turns on ~50us after rising reset when RPM running, or on for ~1 second after power-on reset no RPM
 fuel pump turns on after HYB-39 goes to 1kHz, then primes for ~1 second before going off
 fuel pump turns off ~1 second after rpm goes to 0
   look like fuel pump may be directly controlled by hybrid without any PumpOn MCU output signal
Idle Air Control Related
HYB-32  LH2.4 iac out to drive transistor    T301-B (middle power transistor)
 - 0v 0rpm / ~0.7v peak pulses 800+ rpm, PWM
HYB-17  LH2.4 iac_in input from ECU pin      ECU-33
 - IAC 0v to 12v PWM
HYB-22  LH2.4 iac in ?			     MCU-1/P4.0
 - 0v when HYB-17 12v, 5v when HYB-17 0v
HYB-33  LH2.4 iac in?                        MCU-34/P1.2
 - 5v when HYB-17 12v / 0v when HYB-17 0v, pulse width is ~60% of HYB-22 at 0rpm, same PW at higher RPM

O2 Sensor Related
HYB-11  LH2.4 O2 sensor input                ECU-24
 - O2 sensor input, benchtop switch gives: 0.1v/0.45v/0.9v
HYB-27  LH2.4 lambda rich1                    MCU-29/P1.7
 - 0v = rich, O2 > 0.60v / 5v = not rich, O2 < 0.5v
HYB-28  LH2.4 lambda rich2                   MCU-30/P1.6
 - 0v = rich, O2 > 0.68v / 5v = not rich, O2 < 0.59v

5v - 12v Translation
HYB-7   AC switch on input                   ECU-15
 - 0v ac off / 9.6v ac on
HYB-36  LH2.4 ac switch on output            MCU-64/P5.3
 - 5v ac off / 0v ac on

HYB-14  LH2.4 Auto PN switch input           ECU-30
 - 2v PN / 11.3v D
HYB-24  LH2.4 Auto PN switch output          MCU-65/P5.2
 - 5v PN / 0v D

HYB-8   TXD diagnostics input                MCU-22/P3.1
 - Diag box LED - LED turns on when low, 4.7v to 0v
HYB-30  LH2.4 TXD diagnostics in/out         ECU-12   obd box socket 2
 - Diag box socket 2 - 12v normally, 0v when button pushed or LED on

HYB-19  LH2.4 TPS IDLE input                 ECU-2
 - 0v IDLE, 11v cruise
HYB-21  LH2.4 TPS IDLE output                MCU-67/P5.0
 - 5v IDLE, 0v cruise

HYB-15  LH2.4 TPS WOT input                  ECU-3
 - 0v WOT, 12v cruise
HYB-26  LH2.4 TPS WOT output                 MCU-66/P5.1
 - 5v WOT, 0v cruise

HYB-16  LH2.4 Knock enrichment input         ECU-28
 - 0.9v 0rpm / 7.3v 800rpm+
HYB-25  LH2.4 Knock enrichment output        MCU-61/P5.6
 - 5v 0rpm, 0v 800rpm+

HYB-18  LH2.4 AC clutch on input             ECU-14
 - 0v off / 11.4v on
HYB-23  LH2.4 AC clutch on output            MCU-62/P5.5
 - 0v off / 5v on

BS301/CA3272 600mA driver chip connections:
 - ECU-10 is low speed fan output,   from BS301/CA3272-2  OutA, InA-28 from MCU-23/P3.2
 - ECU-11 is high speed fan output,  from BS301/CA3272-4  OutB, InB-27 from MCU-24/P3.3
 - ECU-31 is ?,                      from BS301/CA3272-12 OutC, InC-17 from MCU-2/P4.1
 - ECU-20 is fuel pump relay output, from BS301/CA3272-14 OutD, InD-16 from T302-C, from HYB-3

(and yes, the ECU-19 coding plug goes through a resistor divider to MCU-14/P6.6/AN6)
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Old Yesterday, 10:36 AM   #31
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Nice thank you, this is very good info. Just for clarification is this a white label 937 with -132 hybrid? And the Hybrid pin 1 is NOT attached to the mcu on this setup? (Don't have an opened 9xx handy.)
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Old Yesterday, 11:50 PM   #32
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Yes, white label '937 with a 129-1 / 132 hybrid, which looks the same as a white label '951 ECU. As far as I could tell, pin 1 is not connected to anything.
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