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96 blazer transmission problems

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  #1  
Old 11-27-2010, 07:51 PM
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Default 96 blazer transmission problems

the service engine light came on and the code is p0719 which means brake switch b circuit low input.so i replaced the brake switch and it seemed to fix the problem,a couple days later it started doing the same thing again.the transmission takes for ever to shift,the cruise dosent work,and when the defrost is on and driving down the road the rpms will go up and down by its self.
 
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Old 11-27-2010, 08:15 PM
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If replacement did not cure the problem, then you likely have a wiring issue.

Here is the procedure applicable to your '96:
P0719 - Brake Switch Circuit Low Input (Switch Stuck On)

Circuit Description
Torque Converter Clutch (TCC) brake switch is used to indicate brake pedal status to PCM. PCM deenergizes TCC solenoid when brake pedal is applied. DTC P0719 detects an open (stuck on) brake switch during acceleration.

Conditions For Setting DTC P0719
DTC will set under the following conditions:
- P0502 (vehicle speed sensor) is not present.
- Vehicle speed is less than 5 MPH.
- Then vehicle speed is 5-20 MPH for 6 seconds, then vehicle speed is more than 20 MPH for 4 seconds.
- All conditions must occur 7 times with brake switch on for more than 15 minutes without PCM detecting voltage input of 2 seconds or more.

MIL will light after first failure signal. TCC brake switch remains closed with brake pedal released, PCM inhibits engagement of TCC solenoid, inhibits 4th gear if in hot mode and freezes shift adapts from being updated.

Diagnostic Procedure
  1. Connect scan tool to DLC. Turn ignition switch to ON position. DO NOT start engine. Using scan tool, record freeze frame and failure records for reference. Data will be lost when DTCs are cleared later in this test.
  2. If an ABS code is set, inspect applicable fuse and replace as necessary. Apply and release brake pedal while observing scan tool. If scan tool displays brake pedal in correct positions, see DIAGNOSTIC AIDS below. If scan tool does not display brake pedal in correct positions, go to next step.
  3. Connect test light between ground and ignition feed circuit terminal at brake switch. If test light is off, repair open in ignition feed circuit, then go to step 9. If test light is on, connect test light between ground and brake switch signal terminal at brake switch. If test light is off, go to step 5. If test light is on, go to next step.
  4. Apply brake pedal. If test light is off, go to step 6. If test light is on, check brake switch signal circuit for short to voltage. Repair circuit as necessary, then go to step 9. If circuit is okay, go to next step.
  5. Ensure brake switch assembly is adjusted properly. Adjust brake switch as necessary, then go to step 9. If adjustment is okay, replace brake switch, then go to step 9.
  6. Release brake pedal. Turn ignition off. Disconnect appropriate PCM connector connected to brake switch signal circuit. See WIRING DIAGRAMS . Turn ignition switch to ON position. DO NOT start engine. Connect test light between ground and brake switch signal terminal of appropriate PCM connector. If test light is on, go to next step. If test light is off, check for open in brake switch signal circuit between brake switch and PCM. Repair as necessary, then go to step 9.
  7. Turn ignition off. Reconnect appropriate PCM connector. Turn ignition switch to ON position. DO NOT start engine. Apply and release brake pedal. If scan tool displays brake pedal in correct positions, see DIAGNOSTIC AIDS below. If scan tool does not display brake pedal in correct positions, go to next step.
  8. Check PCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to next step. If terminals and connections are okay, replace PCM, then go to next step.
  9. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0719". Ensure TCC brake switch signal indicates zero volts for 2 seconds with brake pedal applied. If DTC P0719 is not present, repair is complete. If DTC P0719 is still present, repeat test.


Diagnostic Aids
Check TCC brake switch for proper adjustment. Check PCM calibration for current update. Inspect wiring for poor connections at PCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.
 
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  #3  
Old 11-28-2010, 04:20 PM
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it turns out that one of the wires going to the brake switch pulled out,so i fixed the wire and now the trans shifts like it should.
 
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Old 11-28-2010, 04:33 PM
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Good deal!
 
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