2001 xc-70 P0121 code

[flippedBit]

Hello all,

I know there is a ton of ETM threads and I have probably read most of them but I am stumped.

The other day the car went in to what I now know as 'limp' mode.

I have one of those basic ODB2 Bluetooth readers with the Torque app. It has given me the P0121 fault code. This of course leads me down the ETM rabbit hole.

I pulled the ETM (Yellow label), it was a bit dirty but not too bad, cleaned it up. Checked the startup, it does the closed/whine then back to default position correctly. I then popped the top to test all the voltages.

Code: Select all

3 pin side                                  5 pin side
--------------                              --------------
vss     4.97                                vss 4.96
default 1.32 - 1.35                         default 1.29 - 1.31
closed  0.61 - 0.62                         closed 0.57
open    4.65                                open 4.63

From my understanding those look like good voltages. As I moved the butterfly the voltages seemed smooth although this is just testing with a basic multimeter.

Put it all back together, reconnect the battery, no fault codes car runs fine. Take it for a short drive, come back happy... shut off car, come back 5mins later start car, check engine/runs rough, not happy....

I can clear the fault code and the car runs fine, lots of power etc. and (so far) it only seems the check engine light comes back after restarting the car never while its running.

So I am sort of at a loss and not sure where to look next. Would limping it down to the Volvo dealership to get a proper code read give me any more specifics?

Any thoughts/pointers/ideas would be great.

Thanks.

[RickHaleParker]

P0121 = ECM-904C MIL requested by the throttle unit Faulty signal.

Take the car to Autozone and get a free battery bench check. The code only trips when you try to start the car, It maybe a large voltage drop when cranking that is degrading the signal.

Clean the battery cables terminals.

Get a can of MAF cleaner. Disconnect the wiring harness from the throttle unit and clean the electrical connectors.

[flippedBit]

Thanks for the reply.

Its been a busy weekend. I managed to get the battery load checked and it came up fine. Next on the list is cleaning the MAF.

When you say '...throttle unit and clean the electrical connectors...' are you referring to the connection that is attached to the ETM?

Thanks again.

[RickHaleParker]

When you say '...throttle unit and clean the electrical connectors...' are you referring to the connection that is attached to the ETM?

ETM does stand for Electronic Throttle Module and it is a unit.

[flippedBit]

Haha, fair enough, was just double checking.

[precopster]

That's not a connector on the throttle body. It's a connector block and best left alone.

The connector is located down low on the crossmember. It has 6 pins and is a bear to remove the first time. Usually best to soak with a penetrant fluid and try after a couple of hours.

P0121 is ECM-9150. Sensor 1 low signal or signal missing. Sensor 1 is located on the armature/magnet side of the throttle. Most likely a worn film. A contactless conversion should sort this out however I would have the car read with a higher end scanner or Vida/Dice to see if other throttle codes are present. Some throttle codes are indicative of a failed processor board on the throttle.

[flippedBit]

Yes the one on the cross member was the connector I was referring to. I had the ETM out to check the voltage (which seem good) so I had checked the plug as well, nice and clean.

Just cleaned the MAF sensor and didn't seem to help. I seem unable to reset the fault codes now so I think the only thing left is to try and get the codes read with a better scanner before dropping cash on the conversion or new ETM from xemodex.