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Everything is finally back together, and I am not seeing any oil leaks. Oil victory aside, I am now getting SES errors: P0122 and P1122. I have cleared the codes, but they immediately reset before the car starts. I also attempted to look at the real time throttle % in my scanner, but don't see any movement when pressing on the accelerator. The car starts and appears to run normally.
While the top end was apart fixing the rear intake leak, the throttle body was off the car, but the TPS was not disconnected. I attempted to probe the black and blue wires with a multi-meter set to voltage, but was not getting any reading from the sensor. My hunch at this point is that a wire somewhere was damaged, and I need to pull up the harness and look for damage. The other possibility, which I think is far less likely, is that the sensor has gone bad.
Thoughts? How would you tackle it? (I have a Holley 58MM TB and did have to notch the sensor mounting holes to correct the low voltage previously).
Look at the code descriptions in the factory service manual. That will tell you what voltage sets the codes, and possible causes. Typically if the closed throttle voltage between the dark blue wire and the black wire drops below about 0.20 volts (varies with years) the code will set.
Key on, engine off, connector off the sensor, you should have 5 volts between the gray wire and the black wire. That would confirm the PCM is supplying the reference voltage, and the wires between the PCM and harness connctor are OK.
While the top end was apart fixing the rear intake leak, the throttle body was off the car, but the TPS was not disconnected. I attempted to probe the black and blue wires with a multi-meter set to voltage, but was not getting any reading from the sensor. My hunch at this point is that a wire somewhere was damaged, and I need to pull up the harness and look for damage. The other possibility, which I think is far less likely, is that the sensor has gone bad.
Thoughts? How would you tackle it? (I have a Holley 58MM TB and did have to notch the sensor mounting holes to correct the low voltage previously).
Originally Posted by Injuneer
Look at the code descriptions in the factory service manual. That will tell you what voltage sets the codes, and possible causes. Typically if the closed throttle voltage between the dark blue wire and the black wire drops below about 0.20 volts (varies with years) the code will set.
Key on, engine off, connector off the sensor, you should have 5 volts between the gray wire and the black wire. That would confirm the PCM is supplying the reference voltage, and the wires between the PCM and harness connctor are OK.
Drew, as Fred notes if you are NOT getting 5VDC at the connector using the method he describes than "something" happened to that circuit. If I understand you removed TB but left it plugged in to TPS during your intake manifold gasket fix, right?
If so you may have stretched/pulled one of the wires from its terminal crimp. Back probe the 2 wires before connector to see if the 5VDC is good. If so repin the affected wire. You can remove the pins from these connectors and replace them
I will start this morning checking the reference voltage between the grey and black wires.
I did not leave the harness connected to the sensor, I was just trying to clarify that the sensor had not been removed from the TB to avoid confusion about proper installation of the sensor.
I was unaware of a good method to re-pin and of the connectors. Do you have a good source for new pins? Is there a recommended crimper for the pins? Special tool to remove the pins? I have had about 4 of the connector clips break while working on the car, do you have a good source for new connectors?
There are small probe tools to un-pin them or a very thin flat blade screw driver from the rear of the connector to push the clip on the pin down then pull it out the back. I bought a few pin removal tools. they are like small screw drivers but have a round hollow shaft that goes over the pin on some connectors from the front of connector.
I have replaced a few on the car just the plastic body part because clip tab broke (MAP connector
You can also buy pigtails with connector on the. rockauto has them and some are in help section of auto part stores if splicing wire is your preferred method
Maybe just unplugging the connector the wire somewhere in harness just broke. Back probing will find that.
Fred, are you talking about the 1996 manual? I just looked at the copy I have and found 8A in the contents as electrical diagnosis, but it has 1 blank page and jumps to 8B. This is starting at PDF page 1276.
In any case, I was able to locate damage on the blue wire about 6 inches from the connector, I believe it was pinched by the alternator mount and the accessory bracket:
The car is running, and so far no codes, take to take it out!
I have a copy of the 1996 manual I downloaded several years ago, when each volume and part was a separate file.
I'll ask Gary to take a look at the current combined file.
Fred, the newest copies Gary had posted were all the volumes used in that particular year, combined in one file with the bookmark features added. The bookmarks make searching the manuals easier to find what information your are looking for. If you don't have the updated files, you might want to check them out. You'll need to open the files with an Acrobat reader program or other program that is capable of using the bookmark feature.
Fred, are you talking about the 1996 manual? I just looked at the copy I have and found 8A in the contents as electrical diagnosis, but it has 1 blank page and jumps to 8B. This is starting at PDF page 1276.
OK.... I must have been half asleep yesterday..... Section 8A does not follow Section 8. It is at the end of the "combined" file, or in Volume 2, Part 2, of the individual files, following Section 7 for the Transmission. GM/Helms isn't too into putting things in numerical order.
I keep a copy of the single-page Table of Contents (at the front of the first manual in each set) for each of the years' manuals. Saves a lot of time searching. The later bookmarked versions of the files should make it even easier. But I've been using the individual volume #/part # file version factory manuals as references, to help answer questions for many years, so I know how they are organized (or more correctly "disorganized")..
12-26-2019 | 07:52 PM
