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Help!

Points70

Points70

New member
Alright so I had to change my LIM Gasket and now my car is running rough and with a high idle.

It's throwing codes:

P0121 Throttle Position Sensor circuit A range performance
P0123 Throttle Position Sensor circuit A High P0163 5 volt reference
P0118 Engine coolant temp sensor circuit 1 high

Things I replaced:

Engine Coolant Sensor
Throttle Position Sensor
MAP sensor(because I broke the old one)
EGR gasket
LIM gasket
Valve cover gaskets
Oil pan gasket
Oil pressure sensor
Engine mount
Transmission mount

Things I've checked:

Checked for vacuum leaks and couldn't find any.
Checked ground under ECM, that's fine.
Checked the 5 volt reference from the PCM to the MAP, EGR and fuel pump system seemed ok. I'm unsure about the TPS and engine coolant temp connection. But I checked the resistance between all of the wires in between the TPS and Engine coolant temp sensor. They all have a completed circuit.

What else could make all of these codes throw? My cars been down for almost 2 weeks now.

Do the wires between the TPS and the Engine coolant temp sensor have resistors in them? And if they do can a resistor be bad and the circuit still remain closed?


I would do the IAC relearn and it would drop down the RPM's to a normal range but I have to do it after every first start up. And in gear right off the break it feels like its misfiring and shaking. But no codes are being thrown for any misfires.


Thanks for any help!




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Last edited:


What year of GP are you working on?

Likely the engine coolant temp sensor is junk. They have a high failure rate right out of the box. If you have your old one still I'd use it if it was working.

Have you double checked the firing order? These cars will run with 2 or more wires switched. I know you said no misfire codes but just something I'd double check. There is a diagram here that shows the wire order to be sure.
 
The only reason I replaced the engine coolant sensor was because I accidentally broke the original when taking out the lower intake manifold... So that ones out. And yeah I numbered all of my wires making sure I wouldn't have them out of order but will definitely triple check that.

And I'm hoping it's not the entire harness... That's why I was testing those circuits.

Thanks for the thoughts. I've been caught up with thinking about it I'm just hoping I'm not over looking something like my wires being out of place


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Alright changed the temp sensor and that code stopped. Now it's still the TPS high circuit and the 5 volt reference.


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Also just changed that. Still no change...

Do you know where the ground for the PCM is located? Is there one from it to the chassis?


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I switched my PCM out too with the original one I had and still happening. So it has to be a circuit problem and I wanted to check the grounds first. The one under the icm is fine


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I have and they don't appear damaged at all and the wires appear to be closed circuited but I am buying a new set just to make sure that's not the issue. And when you say grounded via the harness does that mean it's the ring around the harness that you bolt onto the dog bone?


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that is a wire harness holder on the dog bone, its a good idea to see if the holder there ate through the loom and hit the harness too. the plugs to the pcm have ground wires in it, thats how the pcm is grounded.

your main grounds are on the trans bell housing bolts, follow your battery neg cable if you cant find it. its bolted there too.
 
Ok so changed the TPS/ECT connector. It wasn't that. Still throwing a manifold pressure code, ECT high circuit code, TPS performance range code, TPS high circuit code and a 5 volt reference circuit A code...


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Alright I checked all the grounds and they are good. I'm going through the the wires and I'm getting 10volts from the grey wire at the MAP connector and 10volts from the red and black wire at the egr connector. What causes this? Like is the root of the problem in one of those wires down the harness?


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Issue found. Me just rushing and messing up. I over looked the connectors and their placement.


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