General: 70: air mass flow sensor

[Baffler]

Meant to say Engine Coolant Temperature sensor as opposed to ETC Be sure to check this sensor, Jack, as it works in conjunction with the MAF sensor to measure the amount of fuel needed/injected.

[jack taylor]

Hi Baffler, thanks yet again. These are only £20.00 ish on ebay so might just get one anyway. My car is 20 years old so wouldn't be suprised if a lot of things are original. Would you know whether a fault code P0101 could relate to the MAF and the ETC as they are related. thanks jack

[Baffler]

Yes, being 20 years old it will do no harm to check all wiring is intact and void of damage to the aforementioned sensors. With the ignition off, or best to remove the negative (-) battery lead altogether (you'll need your radio code), you can remove the plugs for each sensor and check the condition of the pins/terminals for signs of damage/corrosion. At this point I tend to apply a tiny smear of silicone grease to the pins/terminals, using a small artists paint brush, and then plug/unplug them a few times to help renew the contacts.

If, for example, your ECT sensor is faulty the ECU will automatically think the engine is cold and supply more fuel and adjust the IAC valve (automatic choke) so you can begin to see the importance of this little sensor.


The P0101 is a generic code, generated by a generic OBD tool, for all manufacturers and relates to MAF sensor and the components associated with it.

The Volvo codes for the following components are:
121 - Mass Air Flow (MAF) sensor signal missing or faulty.
121 - Manifold Absolute Pressure (MAP) sensor signal missing or faulty.
122 - Intake Air Temperature (IAT) sensor signal missing or faulty.
123 - Engine Coolant Temperature (ECT) sensor signal missing or faulty.


You're welcome, by the way, this is what the forum is all about. My hope is you get to the bottom of this as cheaply as possible.

[jack taylor]

Hi Baffler, Thank you so much for the detailed info. The original Air mass flow sensor was PBT-GF30 and this was replaced by an identical sensor. The car ran fine for about 100 miles and then poor idling and running, slight increase in fuel consumption and back fire returned together with EML came on again. One sensor failing is ok but not two in a row. Perhaps a Bosch 0280217107 should have been fitted.
To show my absolute ignorance how do I take readings on the terminals with a multi-meter when to do so requires the various sensors to be unplugged and have no current running through them. I fear that if there was an award for idiot of the month I would have no competition. Sorry to bother you with this. jack

[Baffler]

Ok...with the ignition off and engine cold remove the harness plug going to the ECT sensor located on the thermostat housing. You're measuring for resistance of the sensor, not volts coming from the engine wiring harness, so set your multi-meter dial to Ohms (Ω) and place the red lead tip on one terminal of the sensor and the black lead tip on the other terminal...wait a second, or three, for it to register and record the value on the screen.

If there's no value repeat the process a second time in case the tips of the leads didn't make proper contact with the terminals. If there's still no reading the sensor is gone open circuit and needs to be replaced.

You can practice, whilst sitting at your kitchen table sipping your morning coffee, on the original MAF sensor you collected from your mechanic and measure across terminals 1 & 4...you're hoping for 110 Ω with this one.

[Bigfella666]

Jack

Don't you just love folk who understand electrics

Liam, that is a proper fools guide, just for fellas like me !!

[Baffler]

Every day is a school day in my book, Bigfella, no doubt Jack and yourself have abilities beyond mine

[jack taylor]

Hi Bigfella I couldn't agree more[ I am in awe of Liam`s knowledge.

[Baffler]

Originally Posted by jack taylor

Hi Bigfella I couldn't agree more[ I am in awe of Liam`s knowledge.

Humbly honoured by your kind words, Jack, although, there are much more knowledgeable folks on here than me so I stand to be corrected

Any luck with a multi-meter?

[jack taylor]

Hi Liam, credit where credit is due.
Tested both MAFS, original one jumps between 110 and 120 and the new one 110.I assume both are therefore ok.
problems still persist in addition; when in top gear [ auto ] at say 2,000 revs and I lift off the accelerator the revs remain the same until I apply the brakes and are almost stationary when the revs drop and it ticks over at about 1100 to 1200 revs. Still running a bit rich.
It still resembles an old car with a manual choke which is pulled out when the engine is at running temp. Fault codes read again and P0101 still comes up.I would very much appreciate your further views please as to what maybe causing the problem. jack.