TPS issues.

[importwarrior]

http://www.starquestclub.com/forums/viewtopic.php?t=72639

 

http://www.starquestclub.com/forums/viewtopic.php?t=72707

 

tps i believe is pin 15 on the ECU

whats the best way to test the TPS signal at the ecu end of the harness.

can i use an analog meter to test the sweep at the ECU connector?

 

this is whats happenning.

 

tps connector disconnected.

ECU connector is plugged in to the ECU

analog meter on pin 15

other lead of meter to ground.

RESULT:

i believe i am getting 9 ohms on the meter.

 

 

next test that was performed.

ECU connecter disconnected. not in ECU

long wire attached at TPS connector.

other end of long wire near ECU connector.

meter touching the long wire going to TPS connector.

other lead at pin 15.

RESULTS:

the meter shows zero ohms.

 

 

what should i see as far as results.

 

any help would be nice.

 

does this mean ECU is toast?

 

thanks from BUZZ.

 

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Warm up the engine fully, then shut it off.

 

Hook a voltmeter (not ohmmeter) to the green+white wire going to the ECU. On the 87-later ECUs, it'll be on the larger connector about 3 pins in from one end if I remember correctly. Run the voltmeter black wire to a good chassis ground, such as the small wire on one of the ECU mounting screws.

 

Turn the ignition key ON but don't start the engine. You should see some small voltage, around 0.5 volts. SLOWLY press the throttle pedal while watching the voltmeter. The voltage should smoothly increase to at least 3.5 volts, possibly as much as 5.0 volts, in sync with the pedal. This test is easier to do with an analog (needle-pinter type meter, as opposed to a digital meter) where you can see any jiggling/drops in the needle. If the voltage ever drops a bit (or spikes up) then the TPS has a worn spot in it and must be replaced. Typical wear points: at idle and at the throttle position corresponding to normal cruise driving.

 

You can also remove the TPS but leave the connector plugged into the car harness. Then just move the TPS arm while watching the voltage. Any jerkiness, dropouts, etc. means a bad TPS.

 

mike c.

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Tested it like you described mike c.

Car on run position but not running.

red lead of meter to pin 15 TPS wire on ecu connector

black lead of meter to ground. The analog meter tried to go reverse.

should we test it on ohms or volts.

 

That does not seem to be proper. Maybe I did something wrong.

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

From BUZZ:

Ok. Here's what we got. Sweep tested the tps. Checked out ok. Was getting tps error code. Disconnected battery after replacing. Still getting tps code. Got the car to start, idled about 200-300 rpm. I have a rising rate fuel pressure regulator and the lowest setting I can get is 42 or 43 lbs of fuel pressure. Good battery, the volt meter on the dash reads 10 volts, no higher. Car gets to 3000 rpm and the rpms drop like a rock. Checked both injectors (battery test) and checked ohms on injector clips. All good. Put analog voltmeter to pin 15, grounded the other side. Got 0 ohms. pressed gas pedal, needle went towards negative ohms. Switched the voltmeter leads, put the black one to pin 15, grounded the red one. Got 0.5 ohms. Pressed the pedal, needle moved smoothly up to the other end of the meter. (meter was on ohms 1k). Now what the !!!!!!!

[JAinsworth]

Did you check the ohms for the tps at the tps connector? You should have from 3.5k to 6.5k ohms between terminals #1 (GB) and #3 (GW). Next put the meter on terminals 1 and 2 (GR), slowly operate the throttle valve from fully closed to fully open. The ohms should change smoothly from .5K ohms to the number from the reading of terminal 1 and 3. (The first reading you took). Out of specs or jerky, the tps is bad.

Jimmy

 

Shouldn't you check pin 15 for volts and not ohms? You should get 0.4 to 0.7 V throttle fully closed. 4.5 to 5.5V fully open. (on a warm engine)

Jimmy

[mikec]

When testing "in circuit" like I described, you will use the VOLTMETER portion of the multimeter, do NOT use the OHMS function. When in OHMS mode, multimeters inject a small voltage into the circuit. The intent is this voltage is connected to the component being tested - and connected ONLY to that part! With the TPS installed in the car, the ECU plugged in, etc. there is already voltage on the TPS. So you use the Voltmeter function to monitor that voltage. If you try to use the Ohms function, the voltage injected by the ohmmeter fights the ECU voltage. Bad things can happen to the ECU or the ohmmeter.

 

Also, most analog multimeters use red wires for the positive "+" test lead, and black for negative "-" test leads - when in VOLTMETER or AMMETER mode. However, in OHMS mode, the actual polarity of the voltage being injected by the multimeter into your circuit will be backwards - the red test lead/probe will be negative compared to the black wire. When you stuffed your ohmmeter into the ECU connector, with the ignition key ON, the voltage from the ECU & TPS was "normal" (i.e. positive on the red wire) compared to the small negative voltage injected by the ohmmeter... and that makes the meter read backwards.

 

A few analog meters have a POS/NEG or POLARITY switch... this just flips the red & black wires internally. Make sure that is in the "Normal" or "Positive" position for normal use.

 

mike c.

[buzz]

Ok. Checked the ecu with volts. I was over the 5 volts right away. When pressing the gas pedal, the needle did move smoothly. I also did the sweep test on the tps. That was fine. Anyone have any thoughts on what I should do now??? :hangman:

[importwarrior]

from what i understand. he did the sweep test on the TPS and it was smooth on an analog meter.

 

now that he tested it like Mike C said, it was over 5 volts at the ECU connector to ground before he even put his hoof on the gas pedal.

 

when he pressed the gas pedal it moved a little. and went to a higher voltage than 5 volts.

 

this car has not ran properly in almost 3 years. i would love to see it get fixed.

[mikec]

Try this:

engine cold and shut off... unplug the connector to the TPS.

Hook a voltmeter to:

* voltmeter red/+ wire to the green+red wire in the wiring harness (i.e. the connector hanging from the wire bundle, not the connector hanging from the TPS itself)

* voltmeter black/- wire to the green+black wire in the harness.

 

Now start the engine and let it idle. What is the voltage? If it's not right at 5.0 volts, something is WRONG in the ECU. The ECU outputs a regulated 5.0 signal (called "sensor power") on the green+red wire; green+black is a dedicated "sensor ground" wire back to the ECU. If the ECU's internal voltage regulator has died, you'll get something like 12 volts on those wires.

 

If you do get the correct 5 volts, shut the engine off and then disconnect the battery. Then disconnect the ECU. Leave the TPS unplugged still.

Now use an ohmmeter to measure the resistance between the green+black wire and the green+white wire. It should be INFINITE ohms (open circuit). If you get low resistance, the wiring harness has a short in it.

If you're using a quality digital meter (not an analog needle/pointer type) plug the ECU back in and retest. You won't get INFINITE ohms this time but it should still be a fairly high resistance. If it's below 10000 ohms the ECU might have a bug... I've never measured one this way so I don't know the "correct" value but it can't be too low or else it'd swamp the TPS output like your car seems to be doing.

 

mike c.

[buzz]

Thanks mike. Will do this weekend.

[importwarrior]

any updates BUZZZZZZZZzzzzz...... Edited April 5, 2008 by importwarrior