TPS voltage ?
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,013
Likes: 0
From: Pa
TPS voltage ?
Finally goy my car running again with a new Optispark, spark module, and coil. Car started up and ran fine. Then, all of a sudden, the car wouldn’t idle unless I got on the throttle. I let it try to idle on its own and it just died. Now it will start and it just dies. If I try to hit some gas it stalls. I tested the fuel pressure and it seems pretty good and holds steady.
Now my question. I pulled off the TPS connector and with the ignition on I get around 5 volts at each terminal. In my manual it says with the Tech 1 that the voltage should drop to around .2 volts. I don’t have a Tech 1 and am measuring it with a DVM. Anyways, the test says that if I have 5 volts at each side that my wires are either shorting or that the ECM is no good. Am I doing the test correctly with the DVM?
:confused:
Now my question. I pulled off the TPS connector and with the ignition on I get around 5 volts at each terminal. In my manual it says with the Tech 1 that the voltage should drop to around .2 volts. I don’t have a Tech 1 and am measuring it with a DVM. Anyways, the test says that if I have 5 volts at each side that my wires are either shorting or that the ECM is no good. Am I doing the test correctly with the DVM?
:confused:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: TPS voltage ? (Quasar92Blue)
One wire is signal common and should read 0Vdc to chassis ground, one wire is the +5Vdc supply and the third wire is signal return from the TPS.
Reconnect the cable to the TPS and either use a MAD signal probe cable or probe the wires with a fine needle point to find which is the signal wire. Then monitor the signal (with respect to signal common) as you manually move the throttle (ignition On but engine off). It should vary smoothly from about 0.54Vdc to 4.5Vdc over the range of movement. A DMM works fine for this test.
Reconnect the cable to the TPS and either use a MAD signal probe cable or probe the wires with a fine needle point to find which is the signal wire. Then monitor the signal (with respect to signal common) as you manually move the throttle (ignition On but engine off). It should vary smoothly from about 0.54Vdc to 4.5Vdc over the range of movement. A DMM works fine for this test.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,013
Likes: 0
From: Pa
Re: TPS voltage ? (65Z01)
Thanks. I’ll try testing it tomorrow. Not meant to be a joke, but I hate probing wires. I feel it lets moisture in and causes problems down the road. :confused:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: TPS voltage ? (Quasar92Blue)
I know what you mean. I've done it but didn't like the idea either, even though it's only a 5Vdc signal. If I didn't have my AutoXray I'd likely get the MAD test harness.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,013
Likes: 0
From: Pa
Re: TPS voltage ? (65Z01)
I know what you mean. I've done it but didn't like the idea either, even though it's only a 5Vdc signal. If I didn't have my AutoXray I'd likely get the MAD test harness.
:cheers:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: TPS voltage ? (Quasar92Blue)
It's a stand-alone scan tool that sells for about $200. It plugs into the ALDL and can be used to pull codes and monitor engine operating parameters. I find it useful in diagnostics as well as tuning fuel to air as I make air flow mods.
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
Re: TPS voltage ? (Quasar92Blue)
As a previous post stated, one wire should be connected to ground, one to the +5 volts from the ECM, and one is the signal to the ECM to give an indication of throttle position.
However, all three wires from the TPS are connected to the TPS buffer also.
This buffer is located near the windshield washer reservoir; it looks like a relay that plugs into a socket. I would unplug that TPS buffer and see if it makes any difference. The buffer is used to pass throttle position information to the ABS/ASR computer for ASR activity. ASR will probably be disabled while you are doing this -- no big deal.
Tom Piper
However, all three wires from the TPS are connected to the TPS buffer also.
This buffer is located near the windshield washer reservoir; it looks like a relay that plugs into a socket. I would unplug that TPS buffer and see if it makes any difference. The buffer is used to pass throttle position information to the ABS/ASR computer for ASR activity. ASR will probably be disabled while you are doing this -- no big deal.
Tom Piper
Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Re: TPS voltage ? (65Z01)
Hey guys, I bought the "auto xray" last weekend at Kragen Auto Supply (out here on the west coast, elsewhere I think it is called Schucks). The cost is $160.+tax. I checked around (including the auto xray websight) and that was the best price I could find. MAD sells it too in their new catalog for around $200. It is mfg specific ie: GM, FORD, CHRYSLER. Also,they are either OBD1 or OBD2 specific.
[Modified by ittlfly, 6:32 AM 3/26/2002]
It's a stand-alone scan tool that sells for about $200. It plugs into the ALDL and can be used to pull codes and monitor engine operating parameters. I find it useful in diagnostics as well as tuning fuel to air as I make air flow mods.
[Modified by ittlfly, 6:32 AM 3/26/2002]
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Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,013
Likes: 0
From: Pa
Re: TPS voltage ? (ittlfly)
Wow, that price doesn’t seem too bad. I thought it would be a lot worse. Well, finally got my work wrapped up for the day, (I think), and I am going to try the tests you guys recommended. I am starting to miss my old Camaro.
For some reason, I really think my ECM is toast. Thanks for the help and I’ll keep you posted.
For some reason, I really think my ECM is toast. Thanks for the help and I’ll keep you posted.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,013
Likes: 0
From: Pa
Re: TPS voltage ? (Quasar92Blue)
Okay, I checked the voltage at the blue wire with ignition on and it was about .7 volts and climbed steadily over 4 volts at WOT. I disconnected the ASR/TPS module and I had the same readings. I took off the ASR/TPS module and when I shook it, it sounded all loose and clunking inside. Could this be my problem??? :confused: :confused: :confused:
Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Re: TPS voltage ? (Quasar92Blue)
Did you check for ground from the TPS? It sounded like you checked the supply 5v and signal to the ECM. I was just wondering if you also checked the path to ground, common? I don't know about the clanking module, but I will be following this closely. :)
Burning Brakes
Joined: Jan 2002
Posts: 893
Likes: 0
From: Liberal Kansas
Re: TPS voltage ? (ittlfly)
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,013
Likes: 0
From: Pa
Re: TPS voltage ? (ittlfly)
Did you check for ground from the TPS? It sounded like you checked the supply 5v and signal to the ECM. I was just wondering if you also checked the path to ground, common?
I don't know about the clanking module, but I will be following this closely. :)
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,013
Likes: 0
From: Pa
Re: TPS voltage ? (Quasar92Blue)
One more thing. When the car was running recently, I pulled off the MAP sensor connector until my check engine light went on. I reconnected it and the light went out. I shut off the car and the ECM did store the code. (One check in the service manual)
Right now, I am not getting any codes at all. The car fires right up and stalls out immediately.
:cry
Right now, I am not getting any codes at all. The car fires right up and stalls out immediately.
:cry
Safety Car
Joined: Jan 2001
Posts: 4,390
Likes: 693
From: Boise ID
Re: TPS voltage ? (65Z01)
When I read about people using a scanner I was always thinking of a tool costing hundreds of dollars. Is this AutoXray the type of scanner that people use? I sure hope so :D
