07 tahoe with po121 code

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Mussin

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I have an 07 tahoe ltz with just over 100,000 miles. The other week the "cel" came on. Then went away a couple of days later. The light will be on for a few days then off the on then off... The car runs the same with the light on or off so i doubt it it the tps sensor. The idle does not vary at all. Truck runs great, only thing that stinks is the remote start won't work with the check engine light on and winter is fast approaching... Any ideas?
 

OR VietVet

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The Throttle position sensor is a potentiometer that measures the amount of throttle opening. As the throttle is opened, the reading (measured in volts) goes up




The powertrain control module (PCM) supplies a 5 Volt reference signal to the throttle position sensor (TPS) and usually a ground also. A general measurement is: at idle = .5 Volts; full throttle = 4.5 Volts. If the PCM detects that the throttle angle is greater or less than it should be for a specific RPM, it will set this code.

Potential Symptoms

Symptoms of a P0121 trouble code could include:
•Malfunction Indicator Lamp (MIL) illumination (Check Engine Light or Service Engine Soon light)
• Intermittent stumble on acceleration or deceleration
• Blows black smoke on acceleration
•No start

Causes

A code P0121 may mean that one or more of the following has happened:
•TPS has intermittent open or short internally
•Harness is rubbing and causing an open or short in the wiring
• Bad connection at the TPS
• Bad PCM (less likely)
• Water or corrosion in connector or sensor

Possible Solutions

1. If you have access to a scan tool, see what the idle and WOT (wide open throttle) readings are for the TPS. Check if they're close to the specifications mentioned above. If not, then replace the TPS and re-check.

2. Check for an intermittent open or short in the TPS signal. To do that, you can't use a scan tool. You'll need an oscilliscope. The reason is because scan tools take samplings of many different readings over just one or two data lines and can miss an intermittent drop out. Hook up your oscilliscope and watch the signal. It should sweep up and down smoothly with no drop outs or spikes.

3. If no problems were noticed, perform a wiggle test. Do this by wiggling the connector and harness while watching the pattern. Does it drop out? If so, replace TPS and re-check.

4. If you have no TPS signal, check for 5 Volt reference at the connector. If it's present, check the ground circuit for open or shorts.

5. Make sure the signal circuit isn't 12V. It should never have battery voltage. If it does, trace circuit for short to voltage and repair.

6. Look for any water in the connector and replace TPS as necessary.

Other TPS sensor and circuit related DTCs: P0120, P0122, P0123, P0124
 
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Mussin

Mussin

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Thanks. I just find it strange how it runs/ idles great with the light on or off??
 

tsuintx

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First thing to do is to clean your throttle body and MAF. Worked with my wife's Tahoe. Been over a week already and no more code.

Not sure if the MAF cleaning is necessary, but since you have to remove the intake tubing, anyway, so might as well. TB was pretty nasty looking.

The idle will be a bit strange after the cleaning, but don't be alarmed. The ECM is relearning and it might take some time. It took about two days for my wife's truck, but it was definitely a bit nerve wracking to see it jump between 1500-2500.
 
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Joew311

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First thing to do is to clean your throttle body and MAF. Worked with my wife's Tahoe. Been over a week already and no more code.

Not sure if the MAF cleaning is necessary, but since you have to remove the intake tubing, anyway, so might as well. TB was pretty nasty looking.

The idle will be a bit strange after the cleaning, but don't be alarmed. The ECM is relearning and it might take some time. It took about two days for my wife's truck, but it was definitely a bit nerve wracking to see it jump between 1500-2500.


Agreed on the MAF, especially if you run a k&n or similar oiled air filter. This was something I had to do regularly on my old truck. You can buy a can of MAF Sensor cleaner and follow the directions on the can.

I never noticed any difference when my CEL light was on or off but did notice a slight increase in mpg's after I cleaned it.
 

Luie

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Having this issue now with the wifeunits Hoe.
 

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