General: Shift lock solenoid

[toddyboy]

hi,
Can anybody tell me what a shift lock solenoid is and what it actually does.

Thanks.

[Jim314]

One can start the engine of an XC90 with an automatic transmission in Park without having a foot on one of the pedals. But to shift out of Park one must have a foot on the brake pedal. I suppose that depressing the brake pedal switches a solenoid in the shifter housing which allows the gear lever to move out of Park.

A separate system prevents shifting out of Park unless the ignition key is in Position II, the run position. This system is mechanical cable which is actuated by a cam in the ignition lock assembly.

[LeyburnSheep]

Hello

2004 V70R, 5 speed geartronic, 56,000 miles

The shift lock solenoid isn't working, but I can't work out why not. Can anyone help, please?

In key position 2, with either the engine running or not, it is possible to move the gear lever out of park, as it is not being locked by the solenoid. There is no 'thunking' noise indicating that the solenoid is working. I have tested the brake pedal switch, which is fine. The brake lights work consistently. No error codes on the dash, nor DTCs.

Is it correct to say that, when operating normally, the solenoid is activated, when the brake pedal is not depressed, thus locking the gear lever? And the action of pressing the brake pedal removes the power from the solenoid, therefore unlocking the gear lever from Park?

I have tested the solenoid in isolation, and it appears to be working fine. Applying +12 Volts to the green cable, ground on the black, results in a consistently strong action. However, measuring the voltage as supplied to it from the car with the key in position 2 results in unexpected values. +9.6 Volts with the brake pedal not pressed, and a slight drop to 9.3 Volts with the brake pedal pressed.

I have confirmed that Fuse 21 is intact, which is the feed to the gear housing electronics and the solenoid.

Any ideas as to what the problem may be, or any suggestions for what else I can check, please?

Cheers,

Dave

[Moose Test]

Purely conjecture on my part but, as a safety interlock, I'd expect the operation to be the reverse of what you describe - the solenoid is NOT powered in the 'locked' position, rather it would be energised to unlock.

Which might then explain why you're able to move out of park without your foot on the brake pedal - you're solenoid is continually powered.

If that's correct, it might indicate a wiring fault (possible short to positive supply) or a Gear Selector Module internal fault.

[SwissXC90]

Park / neutral position (PNP) function
The gear-shift position sensor has a park / neutral position (PNP) function to prevent the engine being started with a gear selected.
This function prevents the engine being started unless the P or N positions are selected. This prevents the car from lurching forwards when started.

For further information, see Design and Function, central electronic module (CEM).


Design and Function, central electronic module (CEM).
The starter motor is on the left-hand side of the engine by the air cleaner (ACL) housing. The starter motor is powered directly from the battery. There is a solenoid on the starter motor to close the circuit. The central electronic module (CEM) activates a relay in the relay box in the engine compartment to act on the solenoid. This supplies the solenoid with power and closes the circuit for the starter motor.

The starter motor turns when the key is turned to position III in the ignition switch.

There are different functions which prevent starting, depending on whether the car has an automatic or manual transmission. The central electronic module (CEM) also has an electronic immobilizer function which communicates with a transponder in the key. For further information about electronic immobilizers, see Design and Function, Electronic immobilizer.

Cars with manual gearboxes have a sensor in the clutch pedal. The clutch pedal must be depressed to allow starting (certain markets)
In cars with type 4T65EV automatic transmissions, a signal is transmitted from the gear-shift position sensor to the transmission control module (TCM) which then sends a directly connected signal to the central electronic module (CEM)
In cars with AW automatic transmissions, a directly connected signal is transmitted directly from the gear-shift position sensor to the central electronic module (CEM).

There are diagnostics for the relay for the starter motor.

[LeyburnSheep]

Originally Posted by Moose Test

Purely conjecture on my part but, as a safety interlock, I'd expect the operation to be the reverse of what you describe - the solenoid is NOT powered in the 'locked' position, rather it would be energised to unlock.

Thanks for your reply and the sanity check. I agree totally with your logic. I am confused (easily done).

Originally Posted by Moose Test

Which might then explain why you're able to move out of park without your foot on the brake pedal - you're solenoid is continually powered.

Again, logical, and would have hoped that this was the case. Unfortunately I know for sure that the solenoid is not powered-up (I removed the 2 connectors), nor is it stuck (the shaft moves with very little resistance). There is a return spring on the left of the solenoid, which ensures that the shaft parks at its un-powered 'at rest' position. When I isolate the solenoid from the car wiring and apply +12 Volts, it quite happily 'thunks' over to the right, engaging with the gear selector, locking it (!?).

Originally Posted by Moose Test

If that's correct, it might indicate a wiring fault (possible short to positive supply) or a Gear Selector Module internal fault.

It's the latter that I really don't want to think about! Sounds expensive. I was hoping that a warning message may have been shown on the dashboard, or a DTC appear, but there's nothing.

Really appreciate your response. It helps re-think what may / may not be happening.

Cheers,

Dave

[LeyburnSheep]

Originally Posted by SwissXC90

Park / neutral position (PNP) function
The gear-shift position sensor has a park / neutral position (PNP) function to prevent the engine being started with a gear selected.
This function prevents the engine being started unless the P or N positions are selected. This prevents the car from lurching forwards when started.

For further information, see Design and Function, central electronic module (CEM).


Design and Function, central electronic module (CEM).
The starter motor is on the left-hand side of the engine by the air cleaner (ACL) housing. The starter motor is powered directly from the battery. There is a solenoid on the starter motor to close the circuit. The central electronic module (CEM) activates a relay in the relay box in the engine compartment to act on the solenoid. This supplies the solenoid with power and closes the circuit for the starter motor.

The starter motor turns when the key is turned to position III in the ignition switch.

There are different functions which prevent starting, depending on whether the car has an automatic or manual transmission. The central electronic module (CEM) also has an electronic immobilizer function which communicates with a transponder in the key. For further information about electronic immobilizers, see Design and Function, Electronic immobilizer.

Cars with manual gearboxes have a sensor in the clutch pedal. The clutch pedal must be depressed to allow starting (certain markets)
In cars with type 4T65EV automatic transmissions, a signal is transmitted from the gear-shift position sensor to the transmission control module (TCM) which then sends a directly connected signal to the central electronic module (CEM)
In cars with AW automatic transmissions, a directly connected signal is transmitted directly from the gear-shift position sensor to the central electronic module (CEM).

There are diagnostics for the relay for the starter motor.

Many thanks for your posting. Much appreciated. I really like these follow-through explanations, as they give a broader picture of what else may be a factor in the problem.

I am wondering whether it is the signal from the gear shift position sensor that is not being received. So the next port of call is that sensor. I would assume that it is a mechanical thing, but need to do some research ...

Cheers

Dave

[Moose Test]

Is this a recent failure? Or has it never worked whilst you've had the vehicle?