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Old 01-29-2019, 05:04 AM   #1
tomasss
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Default B204FT/GT getting rid of the EGTC sensor

To save myself from headaches in the future, I would like to eliminate the EGTC sensor. My exhaust and turbo are much better flowing than the stock version so high temperatures should not be an issue.

Several people mentioned that they successfully removed it, but I haven't found any detailed info. Is that done just by replacing it with resistors? Simple disconnecting is not the way how to do it I guess...

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Old 01-29-2019, 05:05 PM   #2
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it's LH2.4. There is probably a performance chip you could use that ignores the sensor. Check with sbabbs or thelostartof.
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Old 01-29-2019, 06:08 PM   #3
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Well..Jetronic I could probably fake with reflashed firmware, but the sensor is connected to the TCU as well...and honestly until this car is back on the road I want to keep the Jetronic as stock as possible...otherwise if I do too many modifications it might be one big headache to find the cause if there is some issue.

In the meantime I found >this< reply saying that the output is pulse width modulated signal...so one idea is to check what the output is when the engine is cold and try to replicate that with some pulse generator...

Part 268...


Last edited by tomasss; 01-30-2019 at 04:12 AM..
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Old 02-10-2019, 06:01 PM   #4
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Any ideas? Wanted to measure mine but found out it is actually already shot...going to disassemble it and try to make it work at least for the measurement....
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Old 02-11-2019, 04:24 AM   #5
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If you want it to read cold all the time just leave the sensor part not in the hot exhaust manifold. Take it out and bolt it outside there somewhere. If it all worked of course.
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Old 02-11-2019, 07:29 AM   #6
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Sensor is /was expensive from Volvo, like 700€/$. Some say it is K-type thermocouple, so there might be cheaper solutions.

I would throw away all Lh stuff and get more modern ECU.
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Old 02-11-2019, 11:31 AM   #7
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As mentioned, my sensor is shot. No point in keeping it outside of the manifold unless it works.
Also at least for the beginning I don't want to get rid of the LH.
What I was looking for is a frequency/duty cycle of the PWM, so I can easily emulate it with some PWM generator just for now...
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Old 02-11-2019, 04:54 PM   #8
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How does the car run if you unplug that 268? Does it run at all with it not plugged in? What about with the 268 plugged in but no thermocouple hooked to it? Does it run like that? What have you tried? Sounds like it's broke so have you been driving the car like that?
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Old 02-12-2019, 02:17 AM   #9
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ECU master Det13 might be something to generate PWM?
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Old 02-12-2019, 03:32 AM   #10
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Quote:
Originally Posted by tomasss View Post
As mentioned, my sensor is shot. No point in keeping it outside of the manifold unless it works.
Also at least for the beginning I don't want to get rid of the LH.
What I was looking for is a frequency/duty cycle of the PWM, so I can easily emulate it with some PWM generator just for now...
Thermocouples don't generate PWM. I think you are misunderstanding what is being discussed in the other thread you linked to.

Here is some basic knowledge about thermocouples.

You need to find out what millivolt output the factory sensor produced. A green book with the EGR for your car should have a graph.

Then you'll need to match the voltage with a sensor off the shelf.

edit:// Sorry, then you'll need to build a circuit to output the mV you need for the operation you desire.

Last edited by swedefiend; 02-12-2019 at 03:37 AM..
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Old 02-12-2019, 06:50 AM   #11
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Quote:
Originally Posted by sbabbs View Post
How does the car run if you unplug that 268? Does it run at all with it not plugged in? What about with the 268 plugged in but no thermocouple hooked to it? Does it run like that? What have you tried? Sounds like it's broke so have you been driving the car like that?
I bought the car broken. So no idea yet how it drives without it. But as there is this code reserved for EGTC:

A2 (injection) socket - code 344, EGT signal missing or faulty.

I expect to throw it an error if I just disconnect it.
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Old 02-12-2019, 06:51 AM   #12
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Quote:
Originally Posted by swedefiend View Post
Thermocouples don't generate PWM. I think you are misunderstanding what is being discussed in the other thread you linked to.

Here is some basic knowledge about thermocouples.

You need to find out what millivolt output the factory sensor produced. A green book with the EGR for your car should have a graph.

Then you'll need to match the voltage with a sensor off the shelf.

edit:// Sorry, then you'll need to build a circuit to output the mV you need for the operation you desire.
Yeah but this is not a simple thermocouple. It already contains all the electronics so based on the temperature it generates PWM.
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Old 02-12-2019, 08:41 AM   #13
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Quote:
Originally Posted by tomasss View Post
Yeah but this is not a simple thermocouple. It already contains all the electronics so based on the temperature it generates PWM.
I do not believe so... You could be right. It just doesn't seem congruent with what I've learned about Jetronic systems.

Consider this post which mentions the pins concerning your thermocouple (although in the post below, EZK is sending the required signal to pin #28 instead of the thermocouple):

Quote:
Originally Posted by frpe82 View Post
I thought that I might post this, just for information and further thoughts:

EZ116K:

1: OBD diagnostic socket (in some markets: serial interface)
2: Coolant temp sensor
3: Check Engine Light output, shared with ECU pin 22. Signals: 12-off, 1-on
4: PRE-IGNition, output to ECU pin 28. Signals: 0-Preign, 6.5-stable, 12-knock
5: 12v supply, constant
6: 12v supply, switched
7: Throttle idle switch
8: Load Signal Tq, from ECU pin 25
9:
10: Engine speed sensor
11: Engine speed sensor (shield)
12: Knock sensor (shield)
13: Knock sensor
14: EGR, Ground connector on engine (power ground)
15: EGR, converter, control
16: Igntion amplifier drive, trigger
17: Engine speed signal output. Signals: 6.5-cranking, >8-idle
18: Selector wire. Signals: 5v-disabled, grounded-enabled
19: Selector wire. Signals: 5v-disabled, grounded-enabled
20: Ground connector on engine (signal ground)
21:
22: EGR, temperature sensor
23: Engine speed sensor
24:
25:


LH2.4:

1: Engine speed signal input 6.5 - cranking, >8 - idle
2: TPS signal input 0.2 - Idle speed, 4 - Full load
3: TPS signal secondary input 1.0 - Idling, 10 - Full load
4: Power supply +30 input 12
5: Signal Ground 0.0 - Separate from power ground
6: Mass air flow 0.0 - Separate from power ground
7: Mass air flow input 2.0 - Idling, 5.0 - Full Load
8: Mass air flow, burn-off Output 4.0 - At burn-off, 0 -otherwise
9: Power supply from main input 12
10: Low-speed pressure sensor, engine cooling fan
11: A/C Time-delay Relay, High-speed pressure sensor, engine cooling fan
12: Diagnostics lead I/O
13: Temp Sensor input 4(-20C) -0.5(80C)
14: A/C, ACC load Signal input 12-Auto, 0-ECON
15: Jumper for cold start 0-no cold start, 12 cold start
16: Diagnostics Lead I/O
17: Chassis Ground
18: Injectors control signal Output 7.1Hz, 2.4-4.5ms
19: EGR Valve Output 12 - inactivated, <12 active
20: Fuel Pump relay signal 1-activ, 12-Ign on
21: Main relay operating circuit Output 1 - Ignition on, 12 - Ignition off
22: Check Engine Light Output 12-off, 1-on
23: EGR Temp Sensor input 4.5 -EGR closed, <4.5 -Open
24: Oxygen Sensor input 0.6 - 1.0 - Rich, 0.0 - 0.4 - Lean
25: Load Signal Tq EZK/DI Output Freq incr with throttle opening
26: Shift-Up light Output 12 - Not activated,0 - Activated
27: EVAP Canister purge valve Output 12 - Open, 1 - Closed
28: PRE-IGNition, DI/APC input 0-Preign, 6.5-stable, 12-knock
* Turbo+ Knock enrichment, trigger
* (B204FT/GT TCU) EGT sensor, trigger
29: Codification input 12 - Automatic transmission
30: Raising engine idle speed input 12-R,D,1,2,3, 0 - P,N, and manual
31: Consumption signal to EDU Output Freq incr with throttle opening
32: Cold start valve Output Battery voltage - Not activated
33: IAC valve Output 5-11 - Idling, no load
34: Speed Sensor input 6 -Rotating, 0 or 12 - Stationary
35: Power Supply +15 input 12-Ign on


TCU:

1: Turbo control valve (boost solenoid)
2:
3: OBD diagnostic socket
4: Relay, engine cooling fan, Control module ECC, ECU Pin 15
5: Relay, engine cooling fan
6: Blocking relay A/C
7: Throttle position (TP) switch/TP sensor
8: Throttle position (TP) switch/TP sensor
9: Temperature sensor TCU
10: Exhaust gas temperature sensor
11: High-speed pressure sensor, engine cooling fan
12: Low-speed pressure sensor, engine cooling fan
13: Combined instrument, speed sensor
14: Load Signal Tq, from ECU pin 25
15: 12v supply, constant
16:
17:
18:
19:
20: Ground connector on engine (signal ground)
21: Ground connector on engine (signal ground)
22:
23: 12v supply, switched
24: Throttle position (TP) switch/TP sensor, ground
25: Temperature sensor TCU, ground
26:
27:
28:
29:
30: PRE-IGNition, DI/APC Pin 4 input 0-Preign, 6.5-stable, 12-knock
31:
32:
33:
34:
35:
My point being that the items that I've colored in red above are tied together on the schematic which you've provided.

I think it highly unlikely that in one Jetronic system the "styrenhet bränslesystem" (fuel controler) expects PWM on pin 28 and on yet another (likely identical with different firmware) board you can see that it is being fed a voltage sweep.
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Old 02-12-2019, 08:52 AM   #14
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Well, it is definitely not analog signal from the thermocouple that goes out. As the list above says:

* (B204FT/GT TCU) EGT sensor, trigger

So it is not the same as for regular lh2.4.

Btw this is what is inside the sensor



and AU2901D is quad a/d comparator. I will try to convince my friend to measure the output for me.
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Old 02-12-2019, 02:53 PM   #15
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What about using a different LH2.4 ecu and EZK? Maybe the B230FT version with a performance chip would work without too muich rewiring? Something like a 937 and a chipped gold box EZK.
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Old 02-12-2019, 02:58 PM   #16
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I have a few of them, 2 in working cars and another 2 on the shell, which I don't know if they work.
You can swing by and measure them. I have no clue what to do.
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Old 02-12-2019, 03:32 PM   #17
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Quote:
Originally Posted by tomasss View Post
Well, it is definitely not analog signal from the thermocouple that goes out. As the list above says:

* (B204FT/GT TCU) EGT sensor, trigger

So it is not the same as for regular lh2.4.
I believe that each of the inputs listed below:

Quote:
* PRE-IGNition, DI/APC input 0-Preign, 6.5-stable, 12-knock
* Turbo+ Knock enrichment, trigger
* (B204FT/GT TCU) EGT sensor, trigger
are providing identical inputs to the fuel controller:

0.0V - Pre-ignition (increase fuel enrichment)
6.5V - Stable (do nothing)
12.0V - Knock (decrease fuel enrichment)

Just in one case (yours) a thermocouple is monitoring combustion temps and in another, EZK is relaying knock dependent logic to the fuel controller.

Quote:
Originally Posted by tomasss View Post
Btw this is what is inside the sensor



and AU2901D is quad a/d comparator.
^I'm not smrat enough to analyze that Needs more OTC chips for me to cypher.

But... I've had an idea regarding the comparator. Possibly that large chip marked "EGCT 1" is mapping the millivolt input of the thermocouple to the necessary (0, 6.5, 12) volts.

Quote:
Originally Posted by tomasss View Post
I will try to convince my friend to measure the output for me.
This would be incredibly useful.

edit:// Yeah... just had the epiphany where I realize you might be right. Even if it is as simple as telling the fuel controller to enrich (grounding pin 28), the computer may be smart enough to expect a report at intervals (i.e 12,12,12,12,12,6.5,12,6.5,0,0,0,0,6.5,etc) and while this is technically amplitude modulation, you would still need an oscillator to generate a pulsed 0V to pin 28.

Last edited by swedefiend; 02-19-2019 at 11:45 PM.. Reason: Just read Bob's post and realized that I mistyped in my previous edit
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Old 02-19-2019, 05:46 PM   #18
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What exactly was the point of this of these? B230FTs never had them, right?
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Old 02-19-2019, 08:14 PM   #19
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So it seems like you could rig up a circuit with something like an LM317 adjustable voltage regulator. Adjust it for the 6.5v do nothing signal and that should negate the sensor.
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Old 02-19-2019, 08:31 PM   #20
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As an educated guess, the circuit consists of:
- a LTC chip to compensate for the thermocouple junction (EGTC-2)
- a LTC op-amp to condition/boost the thermocouple signal (EGTC-1)
- a Signetics AU2901N quad comparator to generate the output signal (code 8944 = manufactured in 44th week of 1989)

I'd guess that the temperature is sliced into 3 ranges by the quad comparator, with 2 different pulldown resistors being connected to the output depending on the temperature range.

For LH2.4+EZ116K, the EZK grounds the knock signal from EZK to ECU to increase fueling. I think it's just a simple open-collector driver that results in either 12v or ~0v on the knock wire. Does the B204FT use a different version of the LH2.4 box, maybe one that can do a 3-way sensing of the knock signal voltage?

[If you're interested in thermocouple stuff from the late 1980s, try a search for "Linear Technology thermocouple amplifier application note" (LTC is now part of Analog Devices, so it may point you to their web site if they still post the old app notes.)
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Old 02-19-2019, 08:43 PM   #21
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That makes sense in that it is only two states that it reacts to either a logic high or low but when polled and it's ambiguous nothing happens.
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Old 02-19-2019, 11:50 PM   #22
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Quote:
Originally Posted by bobxyz View Post
As an educated guess, the circuit consists of:
- a LTC chip to compensate for the thermocouple junction (EGTC-2)
- a LTC op-amp to condition/boost the thermocouple signal (EGTC-1)
- a Signetics AU2901N quad comparator to generate the output signal (code 8944 = manufactured in 44th week of 1989)

I'd guess that the temperature is sliced into 3 ranges by the quad comparator, with 2 different pulldown resistors being connected to the output depending on the temperature range.

For LH2.4+EZ116K, the EZK grounds the knock signal from EZK to ECU to increase fueling. I think it's just a simple open-collector driver that results in either 12v or ~0v on the knock wire. Does the B204FT use a different version of the LH2.4 box, maybe one that can do a 3-way sensing of the knock signal voltage?

[If you're interested in thermocouple stuff from the late 1980s, try a search for "Linear Technology thermocouple amplifier application note" (LTC is now part of Analog Devices, so it may point you to their web site if they still post the old app notes.)
Advice from someone that actually knows how things work

One thing though... I really have changed my opinion on the input the fuel controller expects on pin 28. I believe the signal is Pulse Amplitude Modulation.

If indeed the fuel controller is expecting a PAM input and it is simply grounded instead, do you think the controller will throw a code for a missing signal?
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Old 02-20-2019, 12:50 AM   #23
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I just ran across this link again while looking at an old EZK thread:
http://www.stonis-world.com/sebconm.html

Try contacting Stoni and see if he can offer a suitable replacement for your EGT sensor that will work with the TCU, or at least explain better what the output signal looks like.
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Old 02-21-2019, 12:11 PM   #24
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Quote:
Originally Posted by shellshock View Post
What exactly was the point of this of these? B230FTs never had them, right?
only present on the 2.0 liter 16V turbo cars. Lets the car run a more aggressive tune without risk of damaging the exhaust manifold and turbocharger.
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Old 02-21-2019, 12:13 PM   #25
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I got a complete 16V turbo car and pulled all the ECU's and sensors etc... I was thinking about trying to use it but I will most likely just use a standalone ECU when its time to use that motor. I dont want to have to deal with having 3 different ECU's (spark, fuel, turbo).
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