Wednesday, September 26, 2012

P2135 on a 2004 Jaguar XJ

A throttle position sensor code, P2135, is a code flashed by the ECM when it sees a problem with the position of the throttle. The throttle has some sort of 'two in one' sensor, and when there is a discrepancy between the two the ECM flashes this code. In other words, in your throttle body's position sensor there is in reality two sensors, with two tracks, when the ECM sees a that one says one thing and the other 'disagrees' then it flashes this code. This is a two trip light, therefore, if you clear the light it doesn't come back after the test is performed twice by the computer, not right away.

So what could be the problem?
  1. Like almost always with car nowadays... software issues
  2. The throttle position sensor (which is not sold separately :(, new throttle body )

  3. The ECM
  4. The wires between the ECM and the Throttle Position Sensor
This is what you have to do:
  1. Upgrade the software, take it to the dealer or a respectable Jaguar shop, upgrade the software and hope the problem goes away.
  2. Disconnect the throttle position sensor, spray some contact cleaner and reconnect it, clear the code and pray it doesn't come back.
  3. If it does, most likely you need a throttle body buts let's continue testing, Go to connector PI26 which is a 4-way black connector that goes to the throttle body and hook up a multimeter's leads to pin 1 and pin 4, without braking anything, you can use paper clips. You should see power.
  4. If you do, and you are still in denial that you need a throttle body, disconnect the battery and the ECM connector, in that order. The ECM connector is a 134 way black connector. Check the resistance between pin 75 on the ECM and pin 3 on the throttle, you should see (almost) 0 Ohms.
  5. Check pin 76 on the ECM for continuity with pin 2 on the throttle, you should see (almost) 0 Ohms. 
  6. If you did all this then you either need a throttle body or an ECM. To test this you need a factory scan tool, which an experienced technician that specializes in Jaguar like me has, but let me tell you this, I've changed quite a few throttle bodies, and never an ECM to address this specific issue. The odds are against it being an ECM... although there is a small chance.
Good Luck!

1 comment:

  1. Having encountered the limp-home mode with "engine system fault, parking brake fault, DSC not available" messages on 3 occasions within 1000 miles on my 2007 3.0 S-Type Jaguar, I had a garage change the complete throttle body assembly. Having read in many posts and forums this part is eye-wateringly expensive, I was amazed to find it cost just £181 from Jaguar in the UK. By the way, it seems Jaguar re-designed the air-intake system on later models of this car, because the throttle body on mine is centrally located on top of the engine, away from any moisture source, whereas it's reported to be right at the back of the engine block on earlier models where it catches lots of rain run-off from the windscreen. However, in spite of replacing the throttle body, the fault came back again last week, 700 miles after the TB replacement. The DTC is P2135 - Accelerator pedal position (APP) throttle position (TP) sensor switch A/B voltage correlation". I'd be very grateful if someone could tell me what is likely to be still causing the fault condition.

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