Problem With Gear Selector

98silvz71 · June 21, 2008

So lately my truck hasn't been showing the gear that it is in. That little line underneath the PRND321. Not a big deal because I can still tell where I'm at when I shift it. But it has stopped locking and unlocking the doors and not allowing the keyless system to work. Its odd and I was wondering if anyone could tell me how to fix it?

EDIT: And just so we are clear its the one down in my signature.

Impalacat · June 22, 2008

I can't answer the question about it not locking or unlocking, but as far as the indicater on you shifter, this might be of help but I don't know if an 88 chevy is the same as yours, but I had a 88 chevy I bought new and the shift indicater wouldn't show me the gear I was in, so I took the dash apart and found as you shifted the indicater was moved by a very thin cable gizzmo and it was broke, I went to the dealer bought the part and replaced it and never had another problem.

MS3DALE · June 25, 2008

Cam,

I answered your PM,But here is a copy of a Bulletin that might be of interest to you....

Service Information

Document ID: 1530039

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#02-07-30-011C: Slow or No Engagement of Automatic Transmission, No Start, Blank PRNDL Display, Flashing PRNDL, DTC P0708, P0872, P0847, P0875, P1711, P1713 or U1000 Set (Diagnose Condition, Repair) - (Jun 21, 2004)

Subject: Slow or No Engagement of Automatic Transmission, No Start, Blank PRNDL Display, Flashing PRNDL, DTC P0708, P0872, P0847, P0875, P1711, P1713 or U1000 Set (Diagnose Condition, Repair According to Procedure)

Models: 2001-2004 Chevrolet Silverado

2001-2004 GMC Sierra

with Allison® LCT1000 Automatic Transmission (RPO M74) and

6.6L Duramax™ Diesel Engine (RPO LB7) or 8.1L Gas Engine (RPO L18)

Condition

Some customers may comment on one or more of the following conditions.

• The PRNDL display is flashing.

• The engine will not start.

• The "Service Engine Soon" Indicator lamp is illuminated.

• The transmission does not shift properly.

• The vehicle will not move, transmission will not engage.

Cause

Moisture contamination within the Park Neutral Position (PNP) Switch may cause this condition. This is sometimes referred to as the Neutral Start Back-up (NSBU) Switch. On a left turn, water spray from the left front tire is directed directly at this switch. Proper installation of the "Front Shield" and "Rear Shield" are essential for proper repairs.

Technician Diagnosis

***This bulletin ONLY applies to vehicles equipped with a two connector PNP switch.***

A complete and through diagnosis must be performed by a qualified electrical technician to determine the cause and avoid needless replacement of good components.

Important: The Transmission Control Module (TCM) and or the Pressure Switch Manifold (PSM) should NOT be replaced unless properly diagnosed. They are probably not the cause of the concern. It is often assumed the module is the cause of the concern when, in fact, it is another component or the wiring between the components that causes the concern.

Important: Remember, everything starts with a properly operating Neutral Start Back Up (NSBU) switch. The NSBU switch has been incorporated into what is now called the Park Neutral Position (PNP) switch. If the PNP switch does not provide the proper voltage signal to the module indicating the transmission is in either Park or Neutral, the module will not allow the starter operation. After the engine is started, and the shift lever is moved to either Reverse or one of the drive positions, the range selected portion of the PNP switch portion provides a voltage input to the module as to what range the driver has manually selected for transmission operation. The module then controls pressures, shift points and other transmission functions based on the voltage input received from the range portion of the PNP switch.

The technician may find one or more of the following conditions. The list of these conditions does not imply any type of frequency or order. They are random events and may occur in any order.

• DTC P0708, Neutral start/backup (PNP or NSBU) switch

• DTC P0847, Pressure Switch Manifold (PSM)

• DTC P0872, Pressure Switch Manifold (PSM)

• DTC P0875, Pressure Switch Manifold (PSM)

• DTC P1711, Pressure Switch Manifold (PSM)

• DTC P1713, Pressure Switch Manifold (PSM)

• DTC U1000, Serial Data Communications

• Blank PRNDL Display

• Flashing PRNDL Display

• Slow or No Engagement of Automatic Transmission

Blank PRNDL Display

A blank PRNDL display may indicate a condition with the PNP switch and/or one or more of the four signal circuits from the PNP to the TCM.

Pin A, Circuit 771 (BLK/WHT)

Pin B, Circuit 773 (GRA)

Pin C, Circuit 776 (WHT)

Pin D, Circuit 772 (YEL)

Or, a blank PRNDL display may also occur if an out of line condition exists with the Serial Data Circuit (CKT 2470, yellow wire) from the TCM to Splice Pack 205.

Diagnostic Tip

Connect the Tech 2® to the vehicle.

Power up the Tech 2®.

Does the Tech 2® communicate with the TCM? If not, inspect the serial data circuit, CKT 2470 (Yellow wire), between the TCM and Splice Pack 205. Specifically inspect connector C106, a five terminal connector located below the left side underhood bussed electrical center, directly beneath the red battery cable terminal connection. Perform a mating terminal pull test on all of the terminals in this connector. Repair as required.

Observe the Gear Selected screen on the scan tool. The following values should be shown on the Tech 2® display and the vehicle's instrument panel cluster (if equipped with the I/P display).

• "8" (shifter should be in the Park position)

• "7" (shifter should be in the Reverse position)

• "5" (shifter should be in the Drive position)

• "3" (shifter should be in the Third gear position)

• "2" (shifter should be in the Second gear position)

• "1" (shifter should be in the First gear position)

• "0" (shifter should be in the Neutral Position)

If the Gear Selected display does not match the shifter position in the vehicle, diagnose using one of the following methods.

• Obtain a new PNP switch kit, P/N 29540479, from the Parts Department.

1. Disconnect the wiring connector from the original transmission mounted PNP switch.

2. Connect the new switch to the wiring connector.

3. Return to Step #4 above and observe the display as you rotate the switch. If all positions indicate properly, refer to the Correction section below.

• Use the DTC P0708 diagnostic chart in Service Information (SI) under Transmission/Transaxle/Automatic Transmission - Allison. Reference SI Document ID #769549 for the wiring schematic for this symptom.

The PNP switch, as referenced in SI, is known as the NSBU switch in the Parts information. It is now serviced with a Park Neutral Position Switch Kit, P/N 29540479.

Flashing PRNDL Display

A flashing PRNDL display may be the result of incorrect sensor inputs or transmission abuse protection modes being received by the TCM. The following are some of these conditions:

• The transfer case is/was in Neutral.

• The transfer case is/was shifted into Neutral when the vehicle is moving.

• A decrease of the input turbine speed was not detected when the gear selector was moved into any gear.

• A low transmission fluid level.

• A misadjusted PNP/NSBU switch.

• Turbine input speed or output speed sensor failure.

• Failures of the shift solenoids to route the transmission oil to the proper clutch assemblies within the transmission.

• Failures of the transmission clutch packs (C1 or C5 for first gear, C3 or C5 for Reverse).

• Failure to detect proper line pressures when a gear range is selected, which may be the result of normal maintenance such as a transmission fluid change having been completed, or the transmission pan was removed for a filter replacement or other type service.

Transmission abuse protection modes are encountered when a customer performs one of the following types of maneuvers:

• Shifting from Neutral to Drive/Reverse when the engine RPM is greater than 1400 RPM.

• Shifting from Drive to Reverse when the throttle position (TPS) is greater than 25%, such as rocking the vehicle when stuck in an attempt to free the vehicle.

• When the transmission output speed is greater than 300 RPM from attempted changes in direction such as Reverse to Drive, Drive to Reverse or Neutral to Reverse shifts.

When the TCM encounters any one of the above conditions, the TCM will flash the PRNDL and default the transmission to Neutral. A flashing PRNDL indicates something is/was incorrect. The transmission may need the attention of a qualified service technician.

Correction

Disconnect the wiring harness from the PNP switch.

Disconnect the shift linkage/cable from the shift lever at the transmission.

With a wrench keeping the shift lever from rotating, remove the nut from the end of the selector shaft.

Use a file to remove any burrs or raised metal where the selector lever was seated against the shoulder of the selector shaft.

Important: If the old PNP switch will not slide from the selector shaft without the effort, the selector shaft may need to be filed to remove flaring on the end of the selector shaft. This is important, installing the new switch onto a selector shaft that has damage will cause damage to the new PNP switch.

Remove the two bolts that attach the PNP switch and remove the switch by sliding it outward over the selector shaft.

Make sure the selector shaft is in the N (neutral) position (using a wrench on the selector shaft flats, rotate the shaft to its furthest clockwise position and then rotate counterclockwise two detents).

Important: If the new PNP switch will not slide onto the selector shaft easily, the selector shaft may need to be filed to remove flaring on the end of the selector shaft. This is important, installing the new switch onto a selector shaft that has damage will cause damage to the new PNP switch.

Slide the new PNP switch over the selector shaft with the neutral assurance bracket 920 facing outward and maintaining the correct PNP switch orientation to the selector shaft. Install and hand tighten the two PNP switch attaching bolts so that the PNP switch and bracket may be rotated within the adjusting slots with some effort.

While holding the neutral assurance bracket in engagement with the PNP switch, tighten the two bolts that attach the PNP switch to the transmission case.

Tighten

Tighten the bolts to 27 N·m (20 lb ft).

Remove and discard the neutral assurance bracket.

Important: Installation of the front shield and rear shields are important. Without proper installation of the shield, a return repair is probable. Follow all directions as listed on the installation instructions sheet included in the Switch kit, P/N 29540479.

Fit the new shield onto the PNP switch so that it fits securely against the switch. Make sure this is done before reinstalling the shift lever.

Reinstall the shift lever. With a wrench keeping the shift lever from rotating, install the nut on the end of the selector shaft.

Tighten.

Tighten the nut to 24 N·m (18 lb ft).

Connect the wiring harness connectors to the PNP switch.

Attach the selector cable to the lever. Check and adjust if needed.

Go back to step 4 of the Diagnostics and insure the Tech 2 readings match the shift lever positions.

Important: Clear all DTCs before returning the vehicle to the customer.

Return the vehicle to the customer.

Parts Information

Part Number

Description

29540479

Switch kit, Park Neutral Position

Parts are currently available from GMSPO.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

K5228

Switch, Park/Neutral Position - Replace

0.5 hr

Add

Diagnosis Time

0.0-0.3 hr

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

cammiller · June 22, 2008

Adrian, your is a cable, Cam's is electronic. The switch is located on the drivers side of the transmission. The shaft for the gear selector goes through the switch to the shift lever.

cammiller · June 24, 2008

I would replace the switch as long as the wiring is not damaged.

gkwoodfloors · August 26, 2008

I would replace your VSS (vehicle speed sensor) in tail shaft of the T case. The tranny uses it to compare RPM and MPH to determine shifts.

98silvz71 · June 22, 2008

It threw a code right after I posted this. I haven't got the code read yet because O'Reillys was already closed. What switch is it and where is it located besides the side.

98silvz71 · June 24, 2008

The codes are P0700: Transmission Control System Malfunction, and P0708: Transmission Range Sensor Circuit High Input.

Lately the truck has had some rather rough shifts. Only once in awhile. The first one I noticed felt like I had ran over a Mazda or something. I shifted from reverse to drive and it was a nasty shift. I cleared the codes and the truck ran for about 30 minutes of driving before it came back on.

EDIT: Just noticed your name was Cam also.

minibike132 · August 26, 2008

On a side note, who thinks we should make a way to find out if a poster has any qualifications to respond to an ask the technician question.

Edit: sorry just feeling a little b***chy today.

cammiller · June 23, 2008

Yes it could. Do you know what code you have?

98silvz71 · June 24, 2008

Could that be what set off the P0700 code and what makes it rough shift? Or am I looking at more here?

And how much is this switch and can you give me a part number?

cammiller · June 22, 2008

I would check the condition of the switch on the side of the transmission. It probably has water and dirt in it.

98silvz71 · June 23, 2008

Adrian, your is a cable, Cam's is electronic. The switch is located on the drivers side of the transmission. The shaft for the gear selector goes through the switch to the shift lever.

Is it possible that this switch could throw a code?