Sep 282016
 

2005 Chevy SilveraoI have diagnostic trouble code P1125 come up what does it mean?


RESPONSE

Code P1125 – Accelerator Pedal Position Sensor Fault

The accelerator pedal position (APP) sensor 1 and the APP sensor 2 are potentiometer type sensors, each with the following circuits:

• A 5-volt reference circuit

• A low reference circuit

• A signal circuit

The control module provides the APP sensors with a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module signal voltages proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed.

The APP sensor 2 signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 1 and the APP sensor 2 signal circuits are out of correlation with each other, DTC P1125 sets.

The Powertrain Control Module (PCM) detects that the difference between Accelerator Pedal Position (APP) sensor 1 and APP sensor 2 is more than the predicted value.

Code P1125 Possible causes

– Faulty Accelerator Pedal Position Sensor
– Accelerator Pedal Position Sensor harness is open or shorted
– Accelerator Pedal Position Sensor circuit poor electrical connection

Code P1125 Diagnostic Chart

Circuit Description

The accelerator pedal position (APP) sensor 1 and the APP sensor 2 are potentiometer type sensors, each with the following circuits:

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

The control module provides the APP sensors with a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module signal voltages proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 1 and the APP sensor 2 signal circuits are out of correlation with each other, Code P1125 sets.

Conditions for Running the Diagnostic Trouble COde

DTC P1518, P2108 or U0107 is not set.
The ignition is in the Crank or Run position.
The ignition voltage is more than 5.23 volts.
The communication between the throttle actuator control (TAC) module and the powertrain control module (PCM) must be valid.

Conditions for Setting the DTC

The PCM detects that the difference between APP sensor 1 and APP sensor 2 is more than the predicted value.

Action Taken When the DTC Sets

The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.

Conditions for Clearing the MIL/DTC

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Step Action Values Yes No
Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

1 Did you perform the Diagnostic System Check – Engine Controls? Go to Step 2 Go to Diagnostic System Check – Engine Controls
2 Record the throttle actuator control (TAC) module calibration with a scan tool.

Does the TAC module calibration match the part number of the TAC module?

Go to Step 3 Go to Step 11
3 Observe the DTC Information with a scan tool.

Is DTC P2120 or P2125 also set?

Go to Diagnostic Trouble Code (DTC) List Go to Step 4
4
  1. Turn OFF the ignition for 30 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the APP Sensors 1 and 2 parameter with a scan tool.

Does the scan tool indicate that the APP sensors 1 and 2 parameters disagree?

Go to Step 5 Go to Intermittent Conditions
5
  1. Turn OFF the ignition.
  2. Disconnect the accelerator pedal position (APP) sensor.
  3. Disconnect the TAC module.
  4. Measure the resistance of the following circuits for each of the APP sensors with a DMM:
The low reference circuit
The signal circuit
The 5-volt reference circuit

Is the resistance more than the specified value for any circuit?

5 ? Go to Step 9 Go to Step 6
6 Test the signal circuit of the APP sensor 1 for a short to the signal circuit of the APP sensor 2. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12 Go to Step 7
7 Test for an intermittent and for a poor connection at the TAC module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12 Go to Step 8
8 Test for an intermittent and for a poor connection at the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12 Go to Step 10
9 Repair the high resistance in the circuit that measured above the specified value. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12
10 Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement.

Did you complete the replacement?

Go to Step 12
11 Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement.

Did you complete the replacement?

Go to Step 12
12
  1. Assemble the vehicle, as necessary.
  2. Clear the DTCs with a scan tool.
  3. Start the engine.
  4. Operate the system in order to verify the repair.

Did the DTC fail this ignition?

Go to Step 2 Go to Step 13
13 Important: Be aware that repairing one individual condition may correct more than one DTC.

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List System OK
Sep 282016
 

2005 Chevy TrailblazerI have a 2003 Chevy trailblazer 4×4 6c. I sprayed carburetor and choke cleaner in the throttle body then it died and now wont start. its been a week.


RESPONSE

Most carburetor and choke cleaner is for external use only and is not flammable. It can be sprayed onto a rag used to wipe the throat of the throttle body. But should not be sprayed into the Throttle body. Starting fluid should be used to spray into an engine as it will evaporate and not foul the spark plugs. You must have fouled out the spark plugs. You will need to remove the spark plugs and inspect them. It is safe to use starting fluid to remove any residue from the spark plugs left from the cleaner you used. With the spark plugs removed, crank the engine over a few times to clear the cylinders from any contaminates(disconnect coil to avoid shock).

Sep 222016
 

1991 Chevy LuminaI have a 1991 Chevy Lumina with multiple issues. The main one is when it started dying on me with no warning just goes from 40mph to 0 quick. I look under the hood saw a half cut cable leading from the motor to another part of the car I taped it up. Then it dies again so I notice hoses near the left front leaking orange/brown liquid downwards. Part of it coming from a grey cap thing. I don’t know why my car goes from working fine for a couple of miles to just dying. Then two days later it starts up then repeats after a couple of miles. Some people say its the alternator but it might be the half cut radio suppression hose or the leaking liquid right? Then I have an issue with the AC it blows warm air then stops blowing but still makes the sound as if its blowing anything. Do i need a new Freon?


RESPONSE

The most common reason for this year vehicle having the issue you described is a failing ignition control module. Once the car has a period of time to cool down it will start and run as normal for a few minutes or longer and then start to die. Replacing the ignition control module should take care of the issue.

The leaking liquid should not have an effect of the engine as you described but it is a good idea to keep an eye on leaks. Check your fluid levels to determine what the fluid is.

As for the air conditioning issue, we have a pretty good step by step troubleshooting procedure to follow.

Sep 142016
 

1990 GMC SierraMy 1990 Chevy sierra  truck has a 5.7l v-8 t.b.i engine, automatic transmission.                                 The engine runs decent cold but when it warms up, it runs poorly. My truck wants to stall when I come to a complete stop. It hesitates during acceleration. The engine has a very pronounced miss once it reaches normal operating temperature. The spark plugs read different on each side of engine, ranging from lean to rich on both sides. My truck engine ran very good until these symptoms presented themselves all at once. I recently replaced the distributor cap and rotor, spark plugs and spark plug wires. I am recently disabled because, in part, to my memory and cannot figure this out. Very frustrated.


RESPONSE

You stated you recently replaced “distributor cap and rotor, spark plugs and spark plug wires”. If the problem started after you worked on it, recheck your work first.

Assuming you replaced these parts after it started giving you trouble the first step would be to extract any existing diagnostic trouble codes from the On Board Computer. As luck would have it you do not need a scan tool for this. You can do it yourself.

Post any codes below in the comments for further information.

No Codes present. The most common cause would be the ignition control module breaking down.


If you suspect a problem in the ignition system, there are certain preliminary checks which you should carry out before you begin to check the electronic portions of the system. First, it is extremely important to make sure the vehicle battery is in a good state of charge. A defective or poorly charged battery will cause the various components of the ignition system to read incorrectly when they are being tested. Second, make sure all wiring connections are clean and tight, not only at the battery, but also at the distributor cap, ignition coil, and at the electronic control module.

  1. Check the cap for tiny holes and carbon tracks as follows.
    1. Remove the cap and place an ohmmeter lead on the cap terminal.
    2. Use the other lead to probe all the other terminals and the center carbon ball.
  2. If the readings are not infinite, the cap must be replaced.

Ignition Control Module Replacement

1.Remove the distributor cap and rotor as previously described.
2.Disconnect the harness connector and pickup coil spade connectors from the module. Be careful not to damage the wires when removing the connector.

Fig. 1: Be sure to coat the mating surfaces with silicone lubricant

ignition control module

 

3.Remove the two screws and module from the distributor housing.
4.Coat the bottom of the new module with dielectric silicone lubricant. This is usually supplied with the new module. Reverse the above procedure to install.

 

 

 

Aug 242016
 

Dash Lights 2004 Chevy Monte Carlo SS My dash lights went out, all other lights work. I had the BCM scanned and no code came up. The fuse’s are all good. When it get dark the head light come on however the shifter & radio lights go dimm.


RESPONSE

There are four fuses that power the instrument cluster/dash lights. Make sure to check all four. If all fuses check good then you may have a sensor issue or wiring issue. If all sensors check OK and wiring checks, then the cluster itself is defective.

Dash Lights/Instrument Cluster Wiring Diagram 2004 Chevy Monte Carlo SS

2004-chevy-monte-carlo-instrument-cluster-1-of-1

Instrument Cluster Removal

Important The ignition switch must be in the OFF position when removing the instrument cluster.

  • Remove the instrument panel (I/P) cluster trim plate. Refer to Trim Plate Bezel Replacement – Instrument Panel (I/P) Cluster .
  • Remove the instrument cluster screws.
  • Pull the instrument cluster towards you and disconnect the electrical connector.
  • Remove the instrument cluster from the I/P.