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Volvo 940 2.3 Non Turbo 1995 - Unusual Pulsing On The CTS Signal #

Posted by Dave Hill on January 1, 2009, 5:01 pm
Message modified by board administrator January 8, 2009, 7:49 am

Hi everyone & Happy New Year

I have a Volvo 940 1995 2.3 non turbo that came in with an intermittent stalling fault. I eventually pulled a coolant temp sensor DTC with autodiagnos & set about a scope capture. I noticed a regular pulsing on the waveform that made me wonder.

I wondered if this maybe a circuit integrity check that the PCM (Powertrain Control Module) performs.

Anyway I haven't seen it before, so I thought someone more experienced may know.

Cheers all

Dave

Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal

Posted by lee mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on January 2, 2009, 1:53 pm, in reply to "1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal"
Lee Mackintosh

so is the voltage spike to quick to alter the fuel mixture (over fuel) as it switches from around 0.8v upto almost 4v which i assume means cold running condition.

The last volvo i had around the same year with similar faults was caused by a multi-function relay (large white one) in fuse box under ashtray.

Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal

Posted by Dave Hill <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2783' width='330' height='300' border=0 style='border:none;'> on January 2, 2009, 6:47 pm, in reply to "Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal"

Hi Lee

I have been informed elsewhere that this is quite normal on this system.

I wondered if any Autodiagnos users know if I should be able to view live data on this system, or is it too old?

In the Engine section I had the following options.....

Read DTC
Clear DTC
Mode 1
Mode 2

(I think that's right)

Mode 2 would cycle a series of actuator functions, but mode 1 didn't seem to do anything.

Cheer for now

Dave

Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal

Posted by lee mackintosh <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1348' width='330' height='300' border=0 style='border:none;'> on January 2, 2009, 7:42 pm, in reply to "Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal"
Lee Mackintosh

i've got Autodiagnos but only ever used it on 2 early volvo's with the large box plugged in between the leads and never got any live data reading on either.

On newer models with the later pod you do seem to get live data so i think it must be the age of the car.

I've never looked through the Volvo data discs i have as autodiagnos made the original equipment so i would think there must be some good info on Vadis info systems.

Re: Volvo 940 2.3 Non Turbo 1995 - Unusual Pulsing On The CTS Signal

Posted by Dave Hill <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2783' width='330' height='300' border=0 style='border:none;'> on January 7, 2009, 9:02 pm, in reply to "Volvo 940 2.3 Non Turbo 1995 - Unusual Pulsing On The CTS Signal"

Hi All

Further to the previous post, I scoped the new genuine coolant temp sensor & the dodgy Intermotor unit......

Intermotor rubbish..........

New Genuine coolant temp sensor.......

Unfortunately the story doesn't end with the faulty coolant sensor. The car keeps intermittently dropping out of closed loop, with the O2 sensor showing rich, along with a DTC of 2-3-2 fuel trim rich/lean at CTP (closed throttle position).

I am having a nightmare with this, as every time the fault occurs & I try to scope the necessary the bloomin thing drops back into closed loop again. I have had the car most of today set up with the scope monitoring MAF CTS & O2 & the sodding thing just will not fault. You can bet your life, as soon as I give the car back, I will get "THE PHONE CALL" the next day! :?

here is the monitoring capture.....

I always seem to struggle with fuel trim codes "too rich". The fuel pump is recently new & fuel pressure at idle is 38 psi.

Has anyone got any suggestions on this one?

Cheers for now

Dave

Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal

Posted by Sean Connelly <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT5507' width='330' height='300' border=0 style='border:none;'> on January 8, 2009, 9:42 am, in reply to "Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal"

Hi Dave,

What was the engine code on this vehicle?

If you selected the correct engine managment system in the menu then the options you get are all that are supported by that system as this is the original factory tool for pre-99 Volvo's after all.

Looking through the manual for this application then Mode 5 is the equivalent of monitor/live data on the older systems (some systems will display it as Monitor Test).

For your reference the modes used on the older systems are as follows:-

Mode 1 (doesn't exist - probably covered by Read/Erase DTCs menu options)
Mode 2 Confirmation of activation of components & functions
Mode 3 Cyclic activation of components & functions
Mode 4 Individual acttivation of components & functions
Mode 5 Read input & output signals
Mode 6 Enter data

If you don't have a copy of the Volvo manual then you should be able to find it on one of your Autodiagnos CDs in the Documentation folder. Its called ManualVolvoE.pdf I can email you a copy if you want.

HTH

Sean

Link: Macclesfield MOT & Service Centre

Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal

Posted by Dave Hill <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT2783' width='330' height='300' border=0 style='border:none;'> on January 8, 2009, 8:28 pm, in reply to "Re: 1995 Volvo 940 2.3 Non Turbo.Unusual Pulsing On The CTS Signal"
Dave Hill

Hi Sean

I am fairly certain that the engine code is B230FB. I will have a loot tomorrow at work for the Volvo manual pdf.

Thanks for the detailed explaino.

Cheers

Dave

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