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240 High idle after highway run lh2.4

Prime240

240 addict
Joined
Feb 8, 2009
Location
Canada
Greetings all
I have been having the following issue for quite some time now with my 1989 240 equipped with lh 2.4:
After a highway run the car idles too high: around 1500rpm
I get the following codes:
3-1-1 speedometer signal absent
2-3-1 adaptive fuel trim too lean or too rich in part-load range

I am familiar with the fact that if you have no speedo signal the car will idle high but I do have a speedo signal... I know how fast I'm going...
Tried different clusters and I still have the same issue
Could it be an ECU problem?
Thank you for your help
 
Greetings all

3-1-1 speedometer signal absent

I am familiar with the fact that if you have no speedo signal the car will idle high but I do have a speedo signal... I know how fast I'm going...
Different circuits.

Wiring diagrams here show connector #233 with 3 wires
1 - 233/1 - blue to the sensor
2 - 233/2 - black to the sensor
3 - 233/3 - red/black to the ignition switch
Plus another *separate* connection - #200 - blue to the Injection ECU terminal #34.

Sensor tells the speedo what to show you.
Blue wire tells the ECU what the speedo is doing.


1989-240-speed-to-ECU.gif
 
Did your car originally have 2.4lh, or does it now have a different cluster to the original one?

With 2.4lh if you drive over about 3k rpm and don’t have the speed signal connected to the ecu, the idle circuit won’t activate properly when you come back down to less than 3k and you’ll get the 1500rpm idle.

Easy to fix. Get a wire with a female spade connector on it and connect it to-

http://forums.turbobricks.com/showthread.php?t=311154

First photo in the above thread, see the two spade connectors on the upper mid-left , just left of the white plastic housing of the speedo, with a piece of tubing around both of them? They’re for the addition of a cruise control, but it’s the same speed signal you need. Connect the spade connector you have to either one, then crimp it to pin 34 for the ecu.

That’s it.

Cheers

Edit:

Here’s another thread with the cruise control connections labelled, but the photo is lower quality and less clear, so I’ll leave the one above for reference.

https://volvoforums.com/forum/volvo-240-740-940-12/gauge-cluster-help-37638/
 
Different circuits.

Wiring diagrams here show connector #233 with 3 wires
1 - 233/1 - blue to the sensor
2 - 233/2 - black to the sensor
3 - 233/3 - red/black to the ignition switch
Plus another *separate* connection - #200 - blue to the Injection ECU terminal #34.

Sensor tells the speedo what to show you.
Blue wire tells the ECU what the speedo is doing.

Thank you. This was actually tested and there is a signal
 
Did your car originally have 2.4lh, or does it now have a different cluster to the original one?
Yes the car has always been lh 2.4 it is not the original cluster in it now but its the same code on it as the original

With 2.4lh if you drive over about 3k rpm and don?t have the speed signal connected to the ecu, the idle circuit won?t activate properly when you come back down to less than 3k and you?ll get the 1500rpm idle.

This is exactly what happens

Thx for the fix idea. I just don't understand why all of a sudden the signal goes missing
 
Agree that?s odd- broken wire somewhere seems unlikely and I?d have thought a cluster with the same code would be the same in every way.

Cheers
 
That number isn't unique to a particular cluster, but describes the match between the speedometer gauge and the tone ring in the differential. K stands for Kount (count) and the number is how many pulses from the differential are expected per unit distance (kilometers in Canada). The entire instrument cluster went through revisions most every year since its intro in 86.

I guess my question would be how you know the signal from the gauge is OK. In my 89s that wire does, I think, have a connector between the gauge and the ECU pin 34 under the glove box. The most often cause of 311 is the chip on the gauge damaged by a momentary connection of this wire to the ignition coil wire meant for the tachometer. Could have happened long ago in the gauge's past life. Damage can be partial, I suppose, so the signal could be weak. Easiest thing to do is try a different gauge (not the whole cluster). A K9800 or a K10042 gauge will work with your car at least enough to prove the cause of your 311.

Of course it could be a problem in the ECU or even in the ECU's harness connector -- say from stuffing a probe into the socket.
 
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^^^Art, where's your picture of gently re-squeezing the speedo edge connector pins?

OP: Do you have cruise control? If so, try disconnecting it and checking any easy-to-get-to wiring. The same VSS signal that goes to the ECU also goes to cruise box.
 
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I guess my question would be how you know the signal from the gauge is OK.
I'm helping prime 240 with his diagnostic. Since don't really have any way to test the signal from the cluster, we rang (with a multimeter) the wire from the cluster to the ECU and we tried 3 different clusters from the same era and code. We have yet to try another ECU which should be done very soon, right Prime240?
 
OP: Do you have cruise control? If so, try disconnecting it and checking any easy-to-get-to wiring. The same VSS signal that goes to the ECU also goes to cruise box.
I do not: car is a low spec Canadian market DL: owned her for 17 years (with a 4 year hiatus) it has undergone a few mods but nothing to the original engine management.



I'm helping prime 240 with his diagnostic. Since don't really have any way to test the signal from the cluster, we rang (with a multimeter) the wire from the cluster to the ECU and we tried 3 different clusters from the same era and code. We have yet to try another ECU which should be done very soon, right Prime240?
Yes!!! your ECU will go in today but I need to find a moment to get her on the highway....
 
Ok so I swapped the ECU with a known good one and went of on the highway: same issue
Car idles at 1500rpm... until I shut it off and on again : then it goes back to normal idle
 
Keep an eye out for two things while swapping ECUs. Look for signs of water (white or blue/green corrosion) and have a close look into the end of the connector under good light for any deformation of the contact pins.

Tickles me to see we're all helping each other here.

Oops, couple minutes too late. :(
 
Make sure the tps sensor clicks back over clicky click when you let off the gas, that and the speed sensor are what tells the puter when to lay off the high revs if you didn't know...

Maybe check it with an ohm meter or a continuity tester.

Here is not a video about that but shows you how to test the sucker with a beeping meter..

<iframe width="560" height="315" src="https://www.youtube.com/embed/0cbr--8QJio" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

Maybe clean the sheet outta ur flametrap also while you fixing crud. Ha..
 
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Ok so I swapped the ECU with a known good one and went of on the highway: same issue
Car idles at 1500rpm... until I shut it off and on again : then it goes back to normal idle

If the alternate ECU is generating the same 311 code, believe it. Figure out where the wiring harness has a problem.
 
Here's roughly what the differential VR sensor signal (blue) and the generated VSS signal to the ECU (magenta) should look like at ~6 mph:



The VSS signal swings ~1volt to ~12volts, but the pulse width is probably too short (~2ms) for it to show up on a basic multimeter. If you have a LED test light, you should be able to see the VSS signal blink the light at 12 blinks per tire revolution. You might need to probe between +12v and VSS, instead of the more normal VSS and ground (check that your LED test light turns on in both directions when probing the battery and swapping +/- posts).

In addition to the wiring harness, the VSS signal is available on the 2 spade connectors just to the left of the speedo when the cluster is viewed from the back. There's often a short piece of hose protecting these 2 spades from accidental mis-connection.

[Note: do NOT try this with an incandescent test light - it may draw too much current and shutdown or damage the VSS circuits.]
 
Make sure the tps sensor clicks back over clicky click when you let off the gas, that and the speed sensor are what tells the puter when to lay off the high revs if you didn't know...

Maybe check it with an ohm meter or a continuity tester.

Here is not a video about that but shows you how to test the sucker with a beeping meter..

<iframe width="560" height="315" src="https://www.youtube.com/embed/0cbr--8QJio" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

Maybe clean the sheet outta ur flametrap also while you fixing crud. Ha..

Not quite. The VSS signal tells the computer you have dropped below a given speed, however, the ECU doesn't know or care whether the TPS is set correctly, or, closes the circuit. All the TPS does is turn on the IAC. The car can have a dead TPS and it won't generate any codes. It will likely stall quite often.
 
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