TPS sensor
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Joined: Jul 2000
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From: Lake Oswego, OR, USA
TPS sensor
Hey guys, i was just out testing my TPS for the first time and its only reading 3.6 volts at WOT. The thing is, if i push the sensor all the way down till it bottoms out on the throttle body manually it only reaches 3.96. Does that mean i need a new sensor or whats up?
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1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218 the usual street racer with a stock chip.
Gained 20HP by porting and polishing my EGR passage.
------------------
1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218 the usual street racer with a stock chip.
Gained 20HP by porting and polishing my EGR passage.
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Joined: Jan 2001
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From: Belleville, IL USA
<font face="Verdana, Arial" size="2">Originally posted by BenDoe:
Hey guys, i was just out testing my TPS for the first time and its only reading 3.6 volts at WOT. The thing is, if i push the sensor all the way down till it bottoms out on the throttle body manually it only reaches 3.96. Does that mean i need a new sensor or whats up?
</font>
Hey guys, i was just out testing my TPS for the first time and its only reading 3.6 volts at WOT. The thing is, if i push the sensor all the way down till it bottoms out on the throttle body manually it only reaches 3.96. Does that mean i need a new sensor or whats up?
</font>
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Joined: Jan 2001
Posts: 1,429
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From: Belleville, IL USA
it comes from your ECM and through the factory wires & connectors. Heat can increase resistance in wires. The voltage getting to your ECM might also be low. Maybe you TPS is fine and your voltage is just a little lower than normal.
did you grind on your throttle-stop so that the blade opens a full 90* yet?
[This message has been edited by The ODB (edited March 03, 2001).]
did you grind on your throttle-stop so that the blade opens a full 90* yet?
[This message has been edited by The ODB (edited March 03, 2001).]
Thread Starter
Member
Joined: Jul 2000
Posts: 179
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From: Lake Oswego, OR, USA
I called a friend of mine and he said to test the wire between the computer and the TPS. He said there should be a number or something on the computer... can somebody tell me what that number is?
------------------
1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218 the usual street racer with a stock chip.
Gained 20HP by porting and polishing my EGR passage.
------------------
1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218 the usual street racer with a stock chip.
Gained 20HP by porting and polishing my EGR passage.
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Joined: Jan 2000
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Ben,
A quick check would be to measure the voltage between the gray and black wires at the ECM. Don't reference the engine ground to measure the voltage.
Also, there is no plausible way to increase the 5VDC reference signal supply. This voltage is supplied from a voltage divider circuit in the ECM, and is regulated very closely by the circuit. If you measure the voltage directly at the ECM, I'lkl bet it's very close to 5.00 VDC.
First check all engine ground straps, the negative battery cable, and the negative connection node on the body near the battery. Once all these connections are clean and tight, you can check resistance of the wiring between the ECM and TPS. You should also check the ground at the ECM. There is a chassis wiring ground connection in the right footwell, near the lower edge of the lower dash mounting point.
The gray wire (5VDC source) at the TPS is connected at terminal 'C14' of the ECM edege connector. You can back-probe the ECM connector without removing it. There should be less than ½ ohm along this wire (and all others in this test). The dark blue signal wire at the TPS is connected to terminal 'C13' at the ECM. The signal ground wire at the TPS (black one) is connected at terminal 'D2' of the ECM. The signal ground should also be very low resistance to the chassis ground, but it might be as much as 5-10 ohms.
If you measure any resistances greater than ½ ohm, try removing and reseating the edge connectors at the ECM, the bulkhead connector in the right kick panel (some older models have this, some don't) and the connector in the engine compartment at the TPS.
If the connectors appear to be clean and seated well, you may have some corrosion at a splice within the wiring harness. The factory was good at hiding splices within the harmess, and they can erode over time. I've found several splices by accident when doing some ECM modification work. They were soldered and taped over right in the factory harness, and the photo shows several of them in a harness I stripped back:
------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now..."
A quick check would be to measure the voltage between the gray and black wires at the ECM. Don't reference the engine ground to measure the voltage.
Also, there is no plausible way to increase the 5VDC reference signal supply. This voltage is supplied from a voltage divider circuit in the ECM, and is regulated very closely by the circuit. If you measure the voltage directly at the ECM, I'lkl bet it's very close to 5.00 VDC.
First check all engine ground straps, the negative battery cable, and the negative connection node on the body near the battery. Once all these connections are clean and tight, you can check resistance of the wiring between the ECM and TPS. You should also check the ground at the ECM. There is a chassis wiring ground connection in the right footwell, near the lower edge of the lower dash mounting point.
The gray wire (5VDC source) at the TPS is connected at terminal 'C14' of the ECM edege connector. You can back-probe the ECM connector without removing it. There should be less than ½ ohm along this wire (and all others in this test). The dark blue signal wire at the TPS is connected to terminal 'C13' at the ECM. The signal ground wire at the TPS (black one) is connected at terminal 'D2' of the ECM. The signal ground should also be very low resistance to the chassis ground, but it might be as much as 5-10 ohms.
If you measure any resistances greater than ½ ohm, try removing and reseating the edge connectors at the ECM, the bulkhead connector in the right kick panel (some older models have this, some don't) and the connector in the engine compartment at the TPS.
If the connectors appear to be clean and seated well, you may have some corrosion at a splice within the wiring harness. The factory was good at hiding splices within the harmess, and they can erode over time. I've found several splices by accident when doing some ECM modification work. They were soldered and taped over right in the factory harness, and the photo shows several of them in a harness I stripped back:
------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now..."
Thread Starter
Member
Joined: Jul 2000
Posts: 179
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From: Lake Oswego, OR, USA
I measured the reistance from one of the black wires on my computer to the ground and it showed 10 ohms of resistance. I tried to trace the ground but it disapeared into the body of the car. Any more hints?
------------------
1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218 the usual street racer with a stock chip.
Gained 20HP by porting and polishing my EGR passage.
------------------
1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218 the usual street racer with a stock chip.
Gained 20HP by porting and polishing my EGR passage.
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