Throttle body not responding to pedal, nor hand manipulation under hood. Codes include: p0121, p0122, p0222, p1121p1647, p1000. Changed TPS and calibrated and cleared codes and memory (positive to negative battery cables touched for 60 seconds). Afterwards, on start up the engine revs u rapidly to WOT and the throttle body still won't respond to pedal. The only code afterwards is p1000. Any feedback appreciated.

1999 Jaguar XJ8L
98,000 miles

Daque

 

p1646 is upstream lambda B heater circuit and that takes some time to come back. p1000 is just ecm systems check. All others are from tps circuit 1 and 2. How did you calibrate the tps ? Are all of the tps voltages correct when plug is connected to the sensor? Is the sensor ground ok ? When key on engine off does the throttlebody squeal constantly ? P0121 shuts off the throttlebody. Is the butterfly stiff to turn via fingers ? Engine should not rev up to the skies if throttlebody is closed. If this is the case, there is massive air leak that passes throttlebody.

 

Ignore TPS etc for now. Fix the P1647 then report back.

(In case there's an air leak or the PCM can't figure what's occurring why would it want to change the throttle position... Give it more working stuff and then find out.)

 

The TPS voltage at the connector with ignition switch on is 4.6-4.8 volts with it disconnected from the sensor. Also, this is a used replacement throttle body as the original one just quit responding, so it was replaced approx. 6-8 months ago. It worked fine at first then the current issue began as 'not responding when pedal depressed' so I replaced the TPS initially on a whim and the current issue began. Thanks.

 

Also, the throttle body butterfly valve moves from closed to wide open once key move to on position before engaging starter.... see pics- 1st is ignition off and 2nd is ignition in on position.

 

also, with key on and engine off there is a constant whirring sound from the TB while butterfly valve is open. I pushed the butterfly valve closed with my hand and the whirring stopped but there is still 4.8 volts at TPS. Also, after clearing codes nd memory, the p1647 is gone and the only code is p1000, so, any more ideas?

 

The normal fuel flow is disrupted with that code

P1647 : ECM HO2 Sensor control malfunction – bank 2 upstream (2/1)

Possible Causes:
1. HO2 Sensor 2/1 heater failure.
2. HO2 Sensor 2/1 sensing circuit: short circuit to ground, short circuit to high voltage, open circuit.
3. ECM Failure.

 

Butterfly should never go to fully open by itself whitout pressing the pedal. Normal feature is quick buttrefly twist when key is turned on.

 

That P1121 DTC is the PPS (Pedal Position Sensor) not the TPS (Throttle Position Sensor). Check out the other side of the TB where the throttle cable hooks up; that's the PPS. Since the PPS tells the ECU how much to open the throttle, it appears there's something very wrong there; the ECU is telling the TB to open up the throttle to wide open.

 

P1647 is making engine management to fail state yes. But it will start and idle normally. It is mostly useless to measure voltages electrical plug un connected. Especially when device is any kind of variable resistor. With these there is always either measuring voltage and or basic pull-up voltage. With connector not connected you will only measure in this tps case one or two 5V input voltages, possible two pull-up voltages and one or two grounds. Always measure this first and then with a load(connector in place).
It can easily be PPS that is faulty and commands butterfly fully open. If that is the case then it is throttlebody time again. Both tps and pps can be measured off the car at home with multimeter.

 

Thanks, and that makes a ton of sense..... crap!

 

also, what r the PPS voltage ranges from idle to WOT?

 

4.99 volts continuuous whether at idle position of WOT.

 

If I have to replace the PCM, is it plug and play or does it meed to be flashed?

 

What pin has 5V ?
When PPS has connector connected there should be low voltage measured at pin 3 against pin 4 and low voltage at pin 2 against pin 4. This when gas pedal is not pressed. Both of these rises when pedal is depressed all up to the close to 5V.
TPS has the same behaviour low voltage at pin 2 against pin 1 and low voltage at pin 3 against pin 1. These rises with butterfly opening.
If I remember right with my car pps circuit 2 never rises over 3V and car works absolute corret. So high is not always 5V.