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Old 04-07-2021, 12:20 PM   #1
Join Date: Oct 2020
Default Lh and Ezk pin resistance readings

Hello to whoever is kind enough to offer some information on an issue I've been struggling with this past year. My vehicle is 1992 240 DL B230f N/A non EGR and i have 2 oddities.

1. In the Bentley manual page 241-15 it lists resistance readings between pin 6 and 7 on Lh-2.4 for air mass meter wire spec to be between 2.5-4 ohms with ignition off. I already checked the Bentley Errata for any known errors with this spec.

Here are my results:
Back probing pin 6 and 7 of connector connected to Lh-2.4 - 26.5 Kohms
Back probing pin 6 of connector connected to Lh-2.4 - 00.3 ohms
Back probing pin 7 of connector connected to Lh-2.4 - 26.7 Kohms
Measuring resistance directly on terminals 6 and 7 themselves on the Lh-2.4 ECU is 26.5 Kohms
Pin 6 on harness connector to ground with harness disconnected from Lh-2.4 0.03 ohms
Pin7 on harness connector to ground with harness disconnected from Lh-2.4 - No Reading at all.

These specs were wrong according to the Bentley so i ordered a new Lh-2.4 ECU and measuring directly on the terminals of the Lh-2.4 ecu before even trying to connect it to the harness in the car and the pins 6 and 7 measured 26 Kohms (26 thousand ohms). Is this what the spec is actually supposed to be and is there another error in the bentley?

Then there is my other oddity.
2. My EZK ignition computer harness connector pin 2 (coolant temperature sensor) reads correctly according to spec (2000 ohms at 75 degrees) when the harness connector is disconnected from the EZK ignition computer while grounding on the EZK harness connector pin 20, or a separate ground on the car. Then, when the harness is connected to the EZK ignition computer, the resistance reading while back probing pin 2 decreases by more than half (to 665 ohms) while grounding on pin 20 or a separate ground point on the car. When i connect to the EZK the coolant temperature sensor resistance goes out of spec on pin 2. Do i have a bad EZK ignition computer as well or is this supposed to happen?

I have read and read on the forums but i cannot for the life of me figure out what is going on with this car since i got it. Leak down and compression tests are nearly perfect using Snap-On testing tools as well as many other tests that i have done. I've shot the parts shotgun at it twice now to make it run correctly but failing each time. As of now it has code 113 on Lh-2.4 and it did have maf sensor burn off signal lost at one point but it is no longer there. The car seems to be down a cylinder at cold starts until it is at operating temp and even then it still has a slight misfire from what i can tell so far. If anyone can help i would greatly appreciate it. If there are any errors in this post i will try and update it as it has taken me nearly a whole day to write this post. Thank you.
Klech is offline   Reply With Quote
Old 04-07-2021, 01:39 PM   #2
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Join Date: Jul 2016
Location: MA/NH

these are old school computers. They do not have high impedance inputs like modern stuff. The measurements should be taken with the computer disconnected. The way the ecus read the sensors internally affects the resistance you measure on the whole circuit when put together.

Also I would almost ignore the resistance readings for the maf. It is a digital sensor and reading the resistance doesn't really tell one much. For the CTS it is an okay diag approach. Or for diagnosing the harness it is okay as well.
1991 244 LH2.4 M46 352k miles
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Old 04-07-2021, 03:31 PM   #3
Join Date: Oct 2020

Thank you very much for your response. So taking a resistance measurement while the harness is connected to the Lh-2.4 or the EZK will yield an insignificant or different resistance measurement when compared to probing the harness connector while it is disconnected from its appropriate computer. This should mean that even if the resistance reading while being connected is drastically different from spec, it is unimportant as long as the sensor and wires are within spec when disconnected.

After reading your response i realized the error seems to not be from the Lh-2.4 ECU but rather pins 2 and 3 on the MAF sensor currently in the car having what seems to be an infinite resistance when in fact it is those terminals (pin 2 and pin 3) on the MAF itself are supposed to measure 2.5-4.0 ohms. The MAF sensor i speaking of is the VEMO brand P/N V95-72-0011 i recently purchased from FCP Euro. I just went out and measured pins 2 and 3 on my old remanufactured bosch MAF and pins 2 and 3 measured within spec. I previously thought the bosch unit i have was defective but this must mean that the problem lies elsewhere since my new VEMO MAF from FCP Euro is obviously defective from new. I will put the bosch in and see what else i can find.
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Old 04-07-2021, 03:38 PM   #4
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Join Date: Jun 2009
Location: Swampscott, 01907

I have always followed the diag flowchart as provided in the Greenbooks. I'll PM you a link.
I AM THE MODAL AMERICAN. Planet money #936.
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Old 04-07-2021, 04:48 PM   #5
Join Date: Oct 2020

Hey shoestring i wasn't able to get the link to open on my computer or phone. I wonder if it was on that Volvo diagram website that got shut down recently. Thank you very much though i really appreciate the effort. If i am able to get the link to work somehow i cant imagine how much that could help me right now.
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Old 04-07-2021, 07:20 PM   #6
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Join Date: Nov 2011
Location: So Cal

Try this link.

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