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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1569 (Engine Controls Diagnostic (DTC P2131 To DTC U0107) -- 5.7L) >> Diagnosis >> DTC U0107 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  This step determines if the IGN relay is suppling a voltage to the THROT CONT fuse.
  2. 5:  Increasing the engine speed to 3,000 RPM aids in locating a shorted throttle actuator motor control circuit. Depending on the polarity of the throttle actuator motor transistors, this DTC may not set with a fault in the control circuits. The throttle actuator motor is a bi-directional DC motor. Raising the engine speed changes the polarity of the transistors in the throttle actuator motor. This occurs because 1 set of the transistors is near 0 volts, and the other set is at high B+. Therefore, if 1 set of transistors is at a low voltage and the corresponding circuit is shorted low, DTC U0107 will not set. When the polarity of the transistors change this DTC sets. If this DTC does not Fail This Ignition, continue to monitor this DTC status while moving related harnesses and connectors.
  3. 29:  When the TAC module detects a condition within the TAC system, more than TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting the components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
DTC U0107

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View References:  Powertrain Control Module (PCM) Connector End Views  , or  Engine Controls 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 
  1. Turn ON the ignition, with the engine OFF.
  2. Remove the cover from the underhood electrical center.
  3. With a test lamp connected to ground, test both sides of the THROT CONT fuse.
Does the test lamp illuminate on at least 1 side of the fuse?		 - Go to Step 3  Go to Ignition Relay Diagnosis
3
  1. Turn OFF the ignition.
  2. With a test lamp connected to ground, test for voltage at the THROT CONT fuse.
Does the test lamp illuminate?		 - Go to Step 22  Go to Step 4 
4 Install a scan tool.
Is DTC P0606 also set?		 - Go to DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610 Go to Step 5 
5 
IMPORTANT: If the Driver Information Center is displaying Reduced Engine Power, go to Step 6.
  1. Start the engine.
  2. Increase the engine speed to 3,000 RPM, if possible.
  3. Observe the diagnostic trouble code (DTC) Info option using the scan tool.
Does the scan tool indicate this DTC failed this ignition?		 - Go to Step 6  Go to Diagnostic Aids
6
  1. Turn OFF the ignition.
  2. Disconnect the throttle actuator motor harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Test for voltage at both throttle actuator motor control circuits. Refer to Circuit Testing in Wiring Systems.
Does the DMM indicate voltage on both circuits above the specified value?		 8 V Go to Step 12  Go to Step 7 
7
  1. Turn OFF the ignition.
  2. Test both throttle actuator motor control circuits for continuity to ground. Refer to Circuit Testing in Wiring Systems.
Does the DMM indicate continuity to ground?		 - Go to Step 10  Go to Step 8 
8
  1. Turn OFF the ignition.
  2. Remove the THROT CONT fuse.
  3. Test the throttle actuator control (TAC) side of the fuse terminal for continuity to ground. Refer to Diagnostic Aids for terminal identification table.
Does the DMM indicate continuity to ground?		 - Go to Step 9  Go to Step 11 
9
  1. Disconnect the TAC module 16-way harness connector.
  2. Test the TAC side of the fuse terminal for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 24 
10
  1. Disconnect the TAC module 16-way harness connector.
  2. Test the throttle actuator motor control circuits for a short to ground at the TAC module 16-way harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 24 
11
  1. Turn OFF the ignition.
  2. Disconnect the TAC module 16-way harness connector.
  3. Test the TAC module ignition feed circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 24 
12
  1. Turn OFF the ignition.
  2. Disconnect the TAC module 16-way connector.
  3. Turn ON the ignition, with the engine OFF
  4. Test for a short to voltage at both Throttle Actuator Motor control circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 13 
13
  1. Turn OFF the ignition.
  2. Disconnect the TAC module 10-way harness connector.
  3. Test for a short between each throttle actuator motor control circuit and all other TAC module circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 14 
14 Test for an open or for high resistance in the TAC module ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 15 
15 Test for voltage on the serial data circuits at the TAC module 16-way harness connector.
Does the DMM indicate voltage within the specified values for both circuits?		 0-4.5 V Go to Step 16  Go to Step 18 
16
  1. Turn OFF the ignition.
  2. Test both serial data circuits at the TAC module 16-way harness connector for continuity to ground.
Does the DMM indicate OL for both circuits?		 - Go to Step 20  Go to Step 17 
17
  1. Disconnect the posertrain control module (PCM) connector containing the TAC module serial data circuits.
  2. Test both serial data circuits at the TAC module 16-way connector for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 18 
18 Test for a short between both serial data circuits and all other circuits at the PCM and TAC module harness connectors. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 19 
19 Test for a short to voltage on both serial data circuits at the TAC module 16-way connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 25 
20
  1. Disconnect the PCM connector that contains the TAC module serial data circuits.
  2. Test each serial data circuit between the TAC module 16-way harness connector and the PCM harness connector for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 21 
21
  1. Connect the PCM.
  2. Turn ON the ignition.
  3. Test for voltage on the serial data circuit at the TAC module 16-way harness connector.
Does the DMM indicate voltage at the specified value?		 0 V Go to Step 25  Go to Step 24 
22
  1. Turn OFF the ignition.
  2. Disconnect the 16-way TAC module harness connector.
  3. Test the TAC module ignition feed circuit for a short to battery voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 23 
23
  1. Turn ON the ignition.
  2. Test both throttle actuator control motor circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 24 
24 Test for poor connections at the TAC module harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 26 
25 Test for poor connections at the PCM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 28  Go to Step 27 
26 Replace the TAC module. Refer to Throttle Actuator Control (TAC) Module Replacement .
Did you complete the replacement?		 - Go to Step 28  -
27 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 - Go to Step 28  -
28
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 29 
29  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
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