1996 855 20v Code P0121 LH 3,2 Ideling at 1500 rpm

Orlille · Post by **Orlille** » 23 Dec 2014, 05:48

Need some tips where to start searching. Anyone know if there is diagnostic code reader that will work on my car?

Post by **Ozark Lee** » 23 Dec 2014, 08:57

Are you sure you have the Jetronic system? By '96 I thought Volvo had completely phased out the LH 3.2 and gone with the Motronic 4.3. The quick way to tell is to pull the ECU box cover and see how many modules are plugged in. The LH 3.2 had two engine modules and a third module for an automatic transmission if your car is so equipped. The Motronic is a single module and then there would be a second module for the automatic transmission - again, if so equipped.

If you do have the LH 3.2 I don't know what reader might work, I have never seen one that had OBD-II capability. How was the current code (P0121) read?

...Lee

Orlille · Post by **Orlille** » 23 Dec 2014, 12:51

Yes, I am sure my module is Jetronic LH 3,2 ( that's what named on it). Get the code from homemade led flashing unit, A very simple one, tink I have a pic, will find out and post it here.

Post by **Ozark Lee** » 23 Dec 2014, 14:37

The P0121 code is an OBD-II code and it is different than the DTC code 1-2-1 that you read with the flasher unit. DTC code 1-2-1 is a MAF sensor code and P0121 is a throttle position sensor code. They don't interchange number for number.

I have seen a dirty IAC valve cause a MAF code and a high idle on the LH 3.2 but a missing MAF signal will do it as well. Does anything change if you just unplug the MAF sensor?

...Lee

Orlille · Post by **Orlille** » 23 Dec 2014, 15:11

Thanks..will try to unplug MAF sensor tomorrow, 11:08 PM here right now, and santa is on his way.

Post by **Ozark Lee** » 23 Dec 2014, 16:45

Orlille wrote:Thanks..will try to unplug MAF sensor tomorrow, 11:08 PM here right now, and santa is on his way.

Hopefully Julenissen arrives safely! Have a Merry Christmas.

...Lee

Orlille · Post by **Orlille** » 27 Dec 2014, 06:01

Is it ok to unplug MAF sensor when engine is running?

Post by **Ozark Lee** » 27 Dec 2014, 08:29

It won't hurt anything but it may stall. If it does nothing (no change) at all then the MAF is probably bad. It will illuminate the lambda light and set a code but that is easily cleared. I have run the LH 3.2 without the MAF plugged in and the throttle response is odd and the idle tends to surge a bit without it.

...Lee

Orlille · Post by **Orlille** » 27 Dec 2014, 09:03

Thanks Lee.. Just unpluged the MAF sensor, and my engine did not like that at all. Next step will be cleaning IAC and lubricate all moving parts..

Post by **FLXC90** » 28 Dec 2014, 17:13

Sounds like fast idle for warm-up RPM, does temperature indicator show normal operation? Perhaps the Engine Coolant Temperature sensor is bad?