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TPS malfunction,P2135, reduced engine power!

F

fishingplus

New Member
Joined
Jan 1, 2005
Messages
4
Hoping anyone can help me.? My 2003 avalanche keeps dropping to reduced engine power everytime I hit the accelerator hard, 2,500 rpm or more, I have to shut it down and restart it to have the power back and reduced engine power to clear.? The engine warning light stays on still.

I had the truck put on a scanner.? It came back with a DTC code of P2135.? The mechanic said the Throttle position sensor isn't reading any mV at all.? It should be reading between 0-5mV when opening opening and closing the throttle.? That is basically the problem that the voltage correlation between the two sensors on the throttle body differ too much so the engine goes to "reduced power"?

It also doesn't read the throttle as ever going to 0% closed.? It only goes to 15% closed when accelertor not depressed, then will read up to 100% when the throttle is opened up to 100% when the gas peddle is pushed down.

No one in town seemed to sell a throttle position sensor.? I finally found one but I can't find where it is located on the throttle body.? There is a black plastic cover on the left of the throttle body, facing engine, that I believe is where the sensor is.? Of course the box has rivets enclosing it so there is absolutly no way to get inside this box without drilling out the rivets.
I am wondering if that is why it was so hard to find the sensor in town.? I wonder if they want me to replace the whole throttle body to replace this sensor (n).
Anybody that can help I would appreciate it.?
 
There also is a brain box on the firewall, driver side engine compartment that controls the throttle. 2 plugs in it. When I had the reduced engine power message, it had to be replaced.
 
    You might try pulling the connection for the TPS @ the Throttle body. Blow it, and the connector out with some compresed air. If some moisture got in there you would see this senario.
JB
 
Repaired a few this way....


2003-2006 Cadillac Escalade

2003-2006 Chevrolet Avalanche, Corvette, Express, Monte Carlo, Silverado, SSR, Suburban, Tahoe, Trailblazer

2003-2006 GMC Envoy, Savana, Sierra, Yukon

2003-2006 Hummer H2

2005-2006 Pontiac GTO

Equipped with a 4.8 5.3 6.0 or 7.0 V-8 Engine




--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A vehicle may be brought into the dealer for a reduced power message, and DTCs P0120, P0220, P1516, P2101, or P2135.

The Throttle Actuator Control (TAC) / throttle body type trouble codes, may be caused by a loose wiring crimp at the throttle body connector, or a broken throttle body circuit.

Recommendation/Instructions:
Complete the current SI diagnostics for any symptoms or trouble codes found. If a intermittent T/P or TAC module type code is occurring complete the inspections below.

Inspect all related throttle body terminals for a loose wiring crimp. The loose crimp may be difficult to find, and the poor connection will be between the terminal and the copper strands of the wire. Wiggle test the individual throttle body circuits to see if the concern can be duplicated.
Inspect the related circuits for broken wires inside the insulation. The outer wire insulation may look fine, but the internal copper strands may be partially broken. Breaks in the wires usually occur within 1 to 4 inches of the throttle body connector. Wiggle testing may also induce a trouble code to set.
On C/K trucks complete SI procedures for voltage drop on grounds G103 and G104. Grounds G103 or G104 may be loose or corroded.
If a terminal crimp or a broken wire has been found, repair or replace only the circuits involved. There is a throttle body pigtail connector available through GMSPO, but installing this pigtail connector may cause other intermittent TAC module/TP codes at a later date. If this pigtail must be used, please follow the SI procedures for Splicing Copper Wire Using Splice Sleeves. (the proper Kent-Moore crimping tool must be used for this repair)

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.


 
You may find your concern in the above, messing with these terminals with the proper tools for removal can cause very expensive damage very fast!!!, I always start with that bulletin first, then follow the flow chart, alomst always the trucks get new throttle body assy's if the above bulletin checks out ok,  The throttle bodys are serviced as an assy, and are only avail. from a dealer.  All my info says that your truck is drive by wire(no throttle cable) and my advise is based on that fact.
 
I had the wire @ G103 fail inside the insulation at the terminal insulation wrap but didn't have the TPS fault.

G103 is the primary PCM ground circuit (in my 03 anyway) and if it opens up intermittently, things get really weird!

It's also a b*tch to access! :7:
 
Thanks for the responses!

Well I took the plug off the throttle body where the six wires come into the throttle body motor.  I cleaned it with aerosal electrical connector cleaner and put some dielectric grease around the plugs. 
Problem still there!
Still looking for an answer before I have to take my truck to the doctor.
 
That was a good procedure but likely internal to one of the sensors.

The sensors are compared to each other in the PCM. The TP sensor is expected to match the actuator's own sensor, within a given tolerance. If one is too worn or dirty, for example, a code will set and the engine power is reduced to a "limp home" level...

Here's GM's description:
---------------------

Document ID# 861357
2003 Chevrolet Avalanche​

Throttle Actuator Control (TAC) System Description

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:

    ■ Accelerator pedal position sensing
    ■ Throttle positioning to meet driver and engine demands
    ■ Throttle position sensing
    ■ Internal diagnostics
    ■ Cruise control functions
    ■ Manage TAC electrical power consumption

The TAC system components include the following:

    ■ The accelerator pedal position (APP) sensors
    ■ The throttle body assembly
    ■ The throttle actuator control module
    ■ The powertrain control module (PCM)

Accelerator Pedal Position (APP) Sensor

The accelerator pedal assembly contains 2 individual APP sensors within the assembly. The accelerator pedal position (APP) sensors 1 and 2 potentiometer type sensors each with 3 circuits:

    ■ A 5-volt reference circuit
    ■ A low reference circuit
    ■ A signal circuit

The APP sensors are used to determine the pedal angle. The control module provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module with signal voltage proportional to pedal movement. Both APP sensor signal voltages are low at rest position and increase as the pedal is applied.

Throttle Body Assembly

The throttle body assembly consists of the throttle body, the throttle position (TP) sensors, and the throttle actuator motor. The throttle body functions similar to a similar to a conventional throttle body with the following exceptions:

    ■ An electric motor opens and closes the throttle valve.
    ■ The throttle blade is spring loaded in both directions and the default position is slightly open.
    ■ There are 2 individual TP sensors within the throttle body assembly.

The TP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:

    ■ A 5-volt reference circuit
    ■ A low reference circuit
    ■ A signal circuit

The TP sensors are used to determine the throttle plate angle. The control module provides each TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensors then provide the control module with signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens.

Throttle Actuator Control Module

The TAC module is the control center for the throttle actuator control system. The TAC system is self-diagnosing and provides diagnostic information to the PCM through a dedicated serial data line. The TAC achieves throttle positioning by providing a pulse width modulated voltage to the TAC as directed by the PCM.

Powertrain Control Module

The PCM determines the driver's intent and then calculates the appropriate throttle response. This information is sent to the TAC module through a dedicated serial data line.

Modes of Operation

Normal Mode

During the operation of the TAC system, several modes or functions are considered normal. The following modes may be entered during normal operation:

    ■ Minimum pedal value--At key-up the PCM updates the learned minimum pedal value.
    ■ Minimum TP values--At key-up the PCM updates the learned minimum TP value. In order to learn the minimum TP value, the throttle blade is moved to the closed position.
    ■ Ice break mode--If the throttle is not able to reach a predetermined minimum throttle position, the ice break mode is entered. During the ice break mode, the control module commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
    ■ Battery saver mode--After a predetermined time without engine RPM, the control module commands the battery saver mode. During the battery saver mode, the TAC module removes the voltage from the motor control circuits, which removes the current draw used to maintain the idle position and allows the throttle to return to the spring loaded default position.

Reduced Engine Power Mode

When the PCM detects a condition with the TAC system the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:

    ■ Acceleration limiting--The control module will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
    ■ Limited throttle mode--The control module will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
    ■ Throttle default mode--The control module will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
    ■ Forced idle mode--The control module will perform the following actions:
          o Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
          o Ignore accelerator pedal input.
    ■ Engine shutdown mode--The control module will disable fuel and de-energize the throttle actuator.

 
I have a 2011 GMC which I just bought a few months ago. My previous vehicle was an 02 Avalanche which I loved and was 10 times the truck this thing is! I got a P2135 code last week on the fwy and had to pull over. After restarting a few times the problem cleared up but the check engine light stayed on . . later on it went off. Today on the way to work it happened again and took it to the dealer. I kinda knew it was a TPS and had bought a new one but hadn't put it on yet.

Dealer calls says its my TPS and its 310 to fix it. I asked isn't it under the 100K warranty and after he checks and calls back he sayd no its not BUT GM extended the warranty on this part and its covered so it was completely FREE! Please if you have this problem ask your dealer to check for this!
 
sperry said:
That was a good procedure but likely internal to one of the sensors.

The sensors are compared to each other in the PCM. The TP sensor is expected to match the actuator's own sensor, within a given tolerance. If one is too worn or dirty, for example, a code will set and the engine power is reduced to a "limp home" level...

Here's GM's description:
---------------------

Document ID# 861357
2003 Chevrolet Avalanche​

Throttle Actuator Control (TAC) System Description

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:

■ Accelerator pedal position sensing
■ Throttle positioning to meet driver and engine demands
■ Throttle position sensing
■ Internal diagnostics
■ Cruise control functions
■ Manage TAC electrical power consumption

The TAC system components include the following:

■ The accelerator pedal position (APP) sensors
■ The throttle body assembly
■ The throttle actuator control module
■ The powertrain control module (PCM)

Accelerator Pedal Position (APP) Sensor

The accelerator pedal assembly contains 2 individual APP sensors within the assembly. The accelerator pedal position (APP) sensors 1 and 2 potentiometer type sensors each with 3 circuits:

■ A 5-volt reference circuit
■ A low reference circuit
■ A signal circuit

The APP sensors are used to determine the pedal angle. The control module provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module with signal voltage proportional to pedal movement. Both APP sensor signal voltages are low at rest position and increase as the pedal is applied.

Throttle Body Assembly

The throttle body assembly consists of the throttle body, the throttle position (TP) sensors, and the throttle actuator motor. The throttle body functions similar to a similar to a conventional throttle body with the following exceptions:

■ An electric motor opens and closes the throttle valve.
■ The throttle blade is spring loaded in both directions and the default position is slightly open.
■ There are 2 individual TP sensors within the throttle body assembly.

The TP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:

■ A 5-volt reference circuit
■ A low reference circuit
■ A signal circuit

The TP sensors are used to determine the throttle plate angle. The control module provides each TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensors then provide the control module with signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens.

Throttle Actuator Control Module

The TAC module is the control center for the throttle actuator control system. The TAC system is self-diagnosing and provides diagnostic information to the PCM through a dedicated serial data line. The TAC achieves throttle positioning by providing a pulse width modulated voltage to the TAC as directed by the PCM.

Powertrain Control Module

The PCM determines the driver's intent and then calculates the appropriate throttle response. This information is sent to the TAC module through a dedicated serial data line.

Modes of Operation

Normal Mode

During the operation of the TAC system, several modes or functions are considered normal. The following modes may be entered during normal operation:

■ Minimum pedal value--At key-up the PCM updates the learned minimum pedal value.
■ Minimum TP values--At key-up the PCM updates the learned minimum TP value. In order to learn the minimum TP value, the throttle blade is moved to the closed position.
■ Ice break mode--If the throttle is not able to reach a predetermined minimum throttle position, the ice break mode is entered. During the ice break mode, the control module commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
■ Battery saver mode--After a predetermined time without engine RPM, the control module commands the battery saver mode. During the battery saver mode, the TAC module removes the voltage from the motor control circuits, which removes the current draw used to maintain the idle position and allows the throttle to return to the spring loaded default position.

Reduced Engine Power Mode

When the PCM detects a condition with the TAC system the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:

■ Acceleration limiting--The control module will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
■ Limited throttle mode--The control module will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
■ Throttle default mode--The control module will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
■ Forced idle mode--The control module will perform the following actions:
o Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
o Ignore accelerator pedal input.
■ Engine shutdown mode--The control module will disable fuel and de-energize the throttle actuator.
Click to expand...
This information is like gold! I know this thread is old but very relevant! Does the new pedal or throttle body need to be programed by a dealer or do they self program by an idling/driving process?

Also, I am reading 5volt at the TB for the A and B power circuit but the A and B control voltages are different. Is that normal?

I hadn't even considered that the TAC module could be bad. Is there a pin out description anywhere to test those voltages?
 
Last edited:
Sperry is no longer with us as he has passed to AVY Heaven.

hence he is in the last membergroup we have = Silent Avalanche In Memoriam
you will notice this by the banner under member name titled:
SILENT AVALANCHE RIP
 
Not the same code but, I was getting the dreaded P1125, off and on and reduced power.
Ended up replacing the pigtail harness on the throttle body connector.
Something about the yellow wire connector and a bad crimp.

Not sure if this applies to you or not.

Codes p1125 and 2120 going to limp mode

The last 2 weeks have been going into limp mode when I get into the throttle, I have scanner so I pull over check the codes with are p1125 and p2120 both seem to lead to throttle position and or pedal position not matching and goes to limp. I can clear them and continue my drive. After reading...
www.chevyavalanchefanclub.com www.chevyavalanchefanclub.com
 
I am 20 years into my AV ownership experience. Sold the 2004 years ago and am still driving my 2013. I have this Reduced Engine Power occasionally, more frequently lately. This is going to sound odd but...

When this happens I give a few hard taps on the positive battery terminal. Why that works to reset things I have no idea. The cable is tight on the terminal. Go figure. I would love to fix it permanently but I don't have the mind space to delve into it.
 
There is also that 175 Amp Mega fuse on the positive terminal/cable on the battery.

I would check that both nuts for that fuse are tight and clean considering what you have described. Also check that the Neg cable on the battery is tight. As you know, be careful working on that Pos terminal with hand tools and keep them from accidentally touching anything metal/ground around there.
 
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