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Ted G.
Ted G., ASE Certified Technician
Category: Chevy
Satisfied Customers: 6159
Experience:  20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness
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2004 chevy trailblazer: the throttle body and the pedal sensor..motors

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i have a 2004 chevy trailblazer and it says reduced engine power, we changed the throttle body and the pedal sensor, it still won't take gas and says reduced engine power? the dealer Lee motors in pineville, ky, said they didn't have time to run down the problem, so i had to pay them 74.00 for nothing, can you help?
You need to know which code is set to determine what may be failed. Did they tell you?
Customer: replied 7 years ago.
There are several failures that can cause reduced power, but you need the code to get started, worse comes to worse take it to Autozone and they can scan it free of charge or call the dealer and ask what they found.
Customer: replied 7 years ago.
my obd scanner had 2 codes p2135 and p0526
If you replaced the throttle body already this is likely your issue:

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.

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.

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.
Customer: replied 7 years ago.
we also replaced the pedal sensor, so what about the 2 codes i mentioned, p2135 and p0526
Well as a matter of fact, there is also a bulletin for the 0526:

#05-06-02-012B: Service Engine Soon (SES) or Check Engine Light On, DTC P0480, P0526/P1481/P1484 Set (Replace Engine Cooling Fan Wiring Harness) - (Oct 19, 2006)

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Subject:Service Engine Soon (SES) or Check Engine Light On, DTC P0480/P0526/P1481/P1484 Set (Replace Engine Cooling Fan Wiring Harness)
Models:2004-2006 Buick Rainier
2002-2006 Chevrolet TrailBlazer, TrailBlazer EXT
2002-2006 GMC Envoy, Envoy XL
2004-2005 GMC Envoy XUV
2005-2006 GMC Envoy Denali, Envoy XL Denali
2002-2004 Oldsmobile Bravada
2005-2006 Saab 9-7X


This bulletin is being revised to add DTC P1484. Please discard Corporate Bulletin Number 05-06-02-012A (Section 06 -- Engine/Propulsion System).


Some customers may comment that the Service Engine Soon (SES) or Check Engine light is illuminated. This condition may be intermittent and upon investigation, the technician may find either DTC P0480, P0526, P1481 or P1484 set.


This condition may be caused by the cooling fan harness chaffing against the plastic guide it routes through. This contact may damage the insulation of the wires enclosed in that harness.


Replace the engine cooling fan harness using the procedure listed below.

  1. Remove the cooling fan. Refer to the Cooling Fan and Shroud Replacement procedure in the Engine Cooling sub-section of SI.
  2. Place the cooling fan assembly on a bench.
  3. Disconnect the harness electrical connector from the cooling fan clutch.
  4. Remove the harness from the plastic guide while feeding the wires out of the slot.
  5. Before installing the new harness, wrap the affected area on the wires with electrical tape to keep the protective sleeve in place. Be sure to keep the tape approximately 25 mm (1 in) away from the connector so the wires can be fed into the slot.
  6. Feed the wires into the slot and install the harness to the plastic guide.
  7. Connect the harness electrical connector to the cooling fan clutch.
  8. Install the cooling fan. Refer to the Cooling Fan and Shroud Replacement procedure in the Engine Cooling sub-section of SI

Here is the illustration of where the chafe happens:
Customer: replied 7 years ago.
this is what the trailblazer is doing when you drop it in gear it want's to quit, if you put in into park or neutral it back fires from the exhaust, when the reduced engine power light comes on (only when on) it won't pull
The 2135 code means the 2 throttle position sensors are reading differently. If you replaced the throttle body with a new one then you can rule out the sensors, so it is likely in the wiring as referenced in the bulletin. If they read differently and confuse the computer it can cause your performance issues and eventually cause the reduced power message.
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