Does the Mn6 tranny have a lock out so you cant shift it into reverse while in forward motion ?

 

Somebody told me it is suppose to have one but the few times I've gone to 5th, I've hit reverse. Just a slight grind, enough to let you know you've hit reverse. If there is a lock out, I don't have it.

 

ttt

 

Nope no reverse lock out! Bean counters again.

 

That is nuts.... isn't there a regulation that requires that?

 

My 2001 has a "Reverse Inhibit Solenoid", and the service manuals show it is installed in both the MN6 and M12 trannys.

You should get a P0801 DTC if the solenoid is not operating correctly.

 

owners manual on my 04 says locks out over 3 mph

 

All C5's have a reverse inhibit solenoid but it frequently is left disconnected during service operations. This will set a code but not turn on the SES light if I recall.

There was once a known problem where a clip holding part of the solenoid fails and the linkage falls out. This ends up in the bottom of the transmission case but does not cause any problem other than reverse lockout not working. It requires removal of the transmission and disassembly to repair.

 

However, on some cars it is intermitten for some reason. On my Y2K vert it always works. While on the '03 Z06 it usually works but sometimes the gate is open and it requires extra care to get into 5th from 4th. Usually when I detect the gate is open (meaning no lockout) I slip from 4th into 6th then back to 5th gear if 6th is too tall. Someday when I have reason to pull the readend, I'll take a look at the lockout solenoid assembly.

Neil

 

This is what my '99 Owner's Manual says:

"Your six-speed manual transmission has a feature that
allows you to safely shift into REVERSE (R) while the
vehicle is rolling (at less than 3 mph (5 km/h)). You will
be locked out if you try to shift into REVERSE (R)
while your vehicle is moving faster than 3 mph
(5 km/h)."

Needless to say I have never actually tested it.

 

Even with the electronic lockout NOT working, it takes like 15 pounds of force to overcome the "mechanical" lockout. That just about takes two hands! What are you guys doing?

The electronic lockout solenoid only lets you engage reverse when it is on. If it is not working, you have to overcome the "mechanical" backup.

Unless, somehow, your electronic lockout is on all the time. Never heard of this, and I would think that it would overheat. You could test for this by finding the fuse and pulling it.

 

The MN6 does have the reverse lockout. As mentioned the solenoid closes the gate above 3MPH. If the solenoid fails or is unplugged then you have a potential problem.

 

I think we're confusing a lock out with an inhibit, a lock out would require you to lift a T handle or ring on the shifter. Is there one there?
An inhibit solenoid can be overcome with about 15lbs of force about 1/10th the force that can be exerted during fast shifting.

 

Hey Bob did you play in the NFL ? You exert 150 lbs force with one arm during fast shifting?

 

Nope, no NFL but did some testing with a strain gaged shifter a few years back and you would be amazed how much load can put through them.

 

After I had my mechanic replace the torque tube bearings in my C5 ZO6, if I shift to far to the right and up, I find gringding gears (reverse) with ease. I don't know about the 15 pounds, but I am really having a time shifting into 5th...a tad too far to the right and I get the "reverse grind." I am convinced that my mechanic forgot to reconnec the reverse inhibit solenoid. I never had this problem until he replaced the bearings in the torque tube.

Zip Fox

 

Here is the service manual description of how the solenoid works:

Reverse Inhibit Description and Operation
The reverse inhibit solenoid is a safety feature which prevents an inadvertent shift into reverse at speeds above 5 km/h (3 mph). The system consist of the following components:

The powertrain control module (PCM).
The reverse inhibit solenoid.
With the ignition ON, battery voltage is supplied directly to the reverse inhibit solenoid. At forward speeds above 5 kp/h (3 mph) the PCM grounds the control circuit of the reverse inhibit solenoid. This energizes the solenoid and mechanically blocks the shift lever from going into the REVERSE position.

If there is something wrong you should get the following code:
DTC P0801

Circuit Description
With the ignition ON battery voltage is supplied directly to the reverse inhibit solenoid. The powertrain control module (PCM) controls the solenoid by grounding the control circuit via an internal switch called a driver. The driver supplies the ground for the component being controlled. Each driver has a fault line which the PCM monitors. When the PCM commands a component ON, the voltage of the control circuit should be low, near 0 volts. When the PCM commands the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the internal fault detection circuit senses a voltage other than what is expected, the fault line status changes, causing DTC P0801 to set. DTC P0801 is a type C DTC.

Conditions for Running the DTC
The engine is running.

Conditions for Setting the DTC
The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
Condition must exist for a minimum of 5 seconds.
Action Taken When the DTC Sets
The PCM stores the DTC information into memory when the diagnostic runs and fails.
The malfunction indicator lamp (MIL) will not illuminate.
The PCM records the operating conditions at the time the diagnostic fails and stores this information in the Failure Records.
Conditions for Clearing the DTC
A last test failed, or current DTC clears, when the diagnostic runs and does not fail.
A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Use the scan tool in order to clear the DTC.
Diagnostic Aids
Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.
For any test that requires probing the PCM or a component harness connector, use the J 35616-A connector test adapter kit. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.
Low system voltage can cause this DTC to set. When reviewing captured data, verify if a low system voltage condition was present at the time the DTC was stored in memory.
For an intermittent condition, refer to Testing for Intermittent and Poor Connections in Wiring Systems
Test Description
The numbers below refer to the step numbers on the diagnostic table.

2. Listen for an audible click when the reverse inhibit solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.

3. Tests for voltage at the coil side of the reverse inhibit solenoid. The ENG IGN 1 fuse supplies power to the coil side of the reverse inhibit solenoid.

5. Verifies that the powertrain control module (PCM) is providing ground to the reverse inhibit solenoid.

6. Tests if ground is constantly being applied to the reverse inhibit solenoid.

Step
Action
Yes
No

1
Did you perform the Diagnostic System Check - Engine Controls?
Go to Step 2
Go to Diagnostic System Check - Engine Controls in Engine Controls - 5.7L

2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, command the reverse inhibit solenoid ON and OFF.
Does the reverse inhibit solenoid turn ON and OFF?
Go to Step 3
Go to Step 4

3
Observe the Freeze Frame and/or Failure records data for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame and/or Failure records data that you observed.
Does the DTC fail this ignition?
Go to Step 4
Go to Testing for Intermittent and Poor Connections in Wiring Systems

4
Turn OFF the ignition.
Disconnect the reverse inhibit solenoid.
Turn ON the ignition, with the engine OFF.
Probe the ignition 1 voltage circuit of the reverse inhibit solenoid with a test lamp that is connected to a good ground.
Does the test lamp illuminate?
Go to Step 5
Go to Step 11

5
Connect a test lamp between the control circuit of the reverse inhibit solenoid and the ignition 1 voltage circuit of the reverse inhibit solenoid.
With a scan tool, command the reverse inhibit solenoid ON and OFF .
Does the test lamp turn ON and OFF?
Go to Step 9
Go to Step 6

6
Does the test lamp remain illuminated with each command?
Go to Step 8
Go to Step 7

7
Test the control circuit of the reverse inhibit solenoid for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 14
Go to Step 10

8
Test the control circuit of the reverse inhibit solenoid for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 14
Go to Step 10

9
Inspect for poor connections at the reverse inhibit solenoid. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 14
Go to Step 12

10
Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 14
Go to Step 13

11
Repair the ignition 1 voltage circuit of the reverse inhibit solenoid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?
Go to Step 14
--

12
Replace the reverse inhibit solenoid. Refer to Gear Select/Skip Shift Solenoid Replacement .

Did you complete the replacement?
Go to Step 14
--

13
Replace the powertrain control module (PCM). Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 5.7L.

Did you complete the replacement?
Go to Step 14
--

14
Perform the following procedure in order to verify the repair:

Select DTC.
Select Clear Info.
Operate the vehicle.
Select Specific DTC.
Enter DTC P0801.
Has the test run and passed?
Go to Step 15
Go to Step 2

15
With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?
Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 5.7L
System OK

Bill

 

Thanks for the info, Bill. I will be goint back to the tranny shop tomorrow and will be going over this stuff. I am sure that they forgot to reconnect the reverse inhibit solenoid. Like I said, I never had this problem until the bearing were replaced on the torque tube. Now I am concerned that in the several times I miss shifted into reverse the grinding sound did not damage my gears. I am so piqued!!!

Zip Fox

 

If your speedo and cruise works it almost absolutely has to be the reverse lockout solinoid. Been there dun that.

Mike

 

I have a 2001 that locks Reverse out.