VACC’s Technical Advisory Service has been receiving regular calls for information on Hyundai ix35 (Tucson) shift lock problems. There seems to be some common issues across the various models, and this system can fail in many ways. This article should give you some diagnostic insights on repairing this often-overlooked, but important safety system.
HISTORY AND CONTEXT
It was approximately 1914 when the first interlock system was fitted to a vehicle to prevent it from moving unintentionally. As time has progressed, many systems have developed, including ignition key interlocks, transmission shifter interlocks, and brake interlocks to serve this purpose. For many years manufacturers were not required to include a transmission shifter interlock. However, some did, and others did not.
The first brake / transmission interlock devices were introduced in the mid-1980s in some Audi models. Once the gear selector is moved into the park position, a locking mechanism will engage to prevent the shifter from being moved unless the key is in the ignition and the brake pedal has been depressed. This dramatically reduces movement, especially if the parking brake is also applied, and both are in serviceable condition.
The introduction of interlocking devices was an attempt to prevent deaths and injuries caused by vehicles accidentally rolling away and either running people over or crushing them against another object. It was identified that a leading cause, and victims of these tragic events were often children left unsupervised in vehicles, who have inadvertently knocked the transmission shifter out of park or released the handbrake.
We have heard reports from the trade that some technicians have found shift interlocking devices disabled with cable ties, or icy pole sticks jammed into the manual override mechanism. See Diagram #1
There could be some very awkward conversations if anything happens, and it comes back that this is what you have done. Even if it was a temporary repair to get the customer out of trouble and you told them about the risks, this situation might come back to haunt you if an accident happens. If the customers don’t want the vehicle repaired correctly you should record these details to cover yourself if anything happens. See Diagram #11
We have previously produced an article on Hyundai and Kia Shift Lock Systems operation and common faults. This article was a general overview of the system and possible mechanical faults with the A6 six-speed automatic transmission. However, it seems that the situation for the ix35 requires more detailed information.
THE ix35
The ix35 name was introduced by Hyundai in 2009 with the launch of the second-generation Tucson crossover, and is only called the ix35 outside South Korea and North America. It has a model code of “LM”, however, there is another variant with a model code of “EL”, which I believe to be for the European market.
There have been five engine options in the Australian market, and the vehicles could be FWD or have an on-demand 4WD system. The general operation of the shift lock mechanism is similar across all these options. Unfortunately, the electrical circuits, wiring colours and components from the OE information seem to be different from the actual cars in Australia, which has made organising an accurate wiring diagram difficult. So, the wiring diagrams in the following pages may or may not be a match for your vehicle.
OPERATIONAL OVERVIEW
The shift lock mechanism uses a solenoid to unlock the shift lever from the park position, which is mounted in the gear shifter assembly in the centre console. Power to the solenoid comes from what Hyundai calls a Smart Junction Box, which is a control unit which also contains the fuses for many other circuits. The Smart Junction Box is mounted under the driver side dashboard. See Diagram #2
Earlier models before 2013 use either the PCM for the petrol engine variants or the TCM for the diesel vehicles to provide a path to earth for the shift lock circuit. In later models from 2013, both the petrol and diesel variants use the BCM to complete the circuit. See Diagram #4
The PCM, TCM or BCM will only allow the shift lock to release once it receives a signal from the brake light switch, mounted on the brake pedal. The brake light switch has dual contacts, one normally open and the other normally closed. The normally open is used for the brake lights, the normally closed is used to send signals to the ABS, EPS and BCM for other purposes. See Diagram #5
There are many possible issues that we have received feedback on, some of the more common faults have been faults in the power supply, faults of the shift lock solenoid, but the most common seems to be a failure of the BCM in the later model variants.
DIAGNOSTIC STEPS
The VACC’s TechAdvisory Service has been receiving calls about Hyundai ix35 not coming out of park regularly. However, it has taken us some time to receive some trade feedback to compile some diagnostic steps based on a repair method that is reliable.
MECHANICAL ISSUES
The first step is to check for mechanical issues. The vehicle owner’s manual should give you the instructions to use the manual shift lock override. If you can do this, and the shift lock disengages and the shift mechanism moves freely, you have eliminated problems with the lever, shift cable and transmission.
POWER SUPPLY
Check the fuse for the shift lock in the Smart Junction Box. In the earlier models, it is the “TPMS” fuse. In later models, it is labelled as “Module 5”. Check the owner’s manual for your vehicle. Ensure that the fuse is OK and that there is always power to the fuse. If not, diagnose and repair the power supply issue first.
We have received feedback from one of our VACC MotorTech subscribers that they had to replace a Smart Junction Box, as it had an internal fault preventing power supply to the shift lock solenoid. See Diagram #2
BRAKE LIGHT SWITCH TESTING
Next, connect a compatible diagnostic tool and check for codes. Unfortunately, the shift lock system is not monitored, so there are no diagnostic codes for the solenoid or its circuit. However, if there are ABS or ESP systems codes relating to the brake light switch, it might be a clue.
Next, look at the live data for both sides of the brake light switch. As there are two contacts within the switch, you should be able to see one turn on and the other turn off as you press the brake pedal. If not, there could be an issue with the switch or its adjustment.
There has been an updated brake light switch released, the old switch has a black connector, and the updated part has a grey one. Check the switch and wiring for any faults and repair or replace as required. See Diagram #6
SHIFT SOLENOID TESTING
There should always be power to the solenoid. To check this, you will have to remove the covers from the centre console, which is straight forward, except for the shifter knob. See Diagram #8
There are no obvious clips or screws, and we have heard many stories of technicians destroying the knob attempting to get it off. A new knob is about $300 new from the dealer. To remove the knob, shift the lever into neutral so the shaft is vertical. Then grab the knob and with brute force, just pull straight up.
This will allow the very strong spring clip inside the knob to open and come off. Be careful not to punch yourself in the face, or anywhere else. With the console removed, the wiring connector for the shift unit is on the left-hand side. Check for power to the connector. See Diagram #7
If there is none, diagnose and repair as required. Then using appropriate tools, earth (ground) the connector from the solenoid, and it should release the mechanism. If not, check the resistance through the solenoid. There is no OE resistance specifications available. However, one of our members checked the resistance of a new solenoid and found 0.2Ω. If there is no circuit, you might need a new solenoid. See Diagram #7
It seems that you can buy an after-market solenoid to fit into the shifter assembly. However, you will need to insert the terminal pins into the connector. We have been told that you must insert the pins correctly as the current will only flow through the solenoid in one way as there is a diode fitted inside the solenoid. See Diagram #7
EARTH (GROUND) CIRCUIT
If there is power to the solenoid and when earthed (grounded), it actuates, this leaves the earth (ground) circuit. The early models could use the PCM or TCM to switch the earth (ground) when the brake pedal is applied, and the later models use the BCM, which seems to be the most common point of failure.
To check the circuit to the BCM, you will have to remove the trim on top of the dash, and the two vents each side of the radio. This will allow you to remove the radio to access the mounting bolts for the BCM. You will then have to remove the trim in front of the gear selector. This will allow you to position the BCM off its mounts, which will allow you to unclip Connector C from the BCM. See Diagram #12
With this connector unplugged from the BCM, you can now turn the ignition on. Using an old school test light with an incandescent globe (or something else with a resistance to prevent a dead short, or at least a fused jumper wire) connected to a known good earth (ground), then probe terminal 6. 
This could be a green wire or a green with black trace, depending on variant. Once earthed (grounded), the solenoid should actuate when the brake pedal is pressed.
If this is the case, a new BCM could be required. If not diagnose and repair the wiring or connectors from the solenoid to the BCM connector and retest. Then check the BCM earth (ground) point. If this is OK, the BCM might be your problem. See Diagram #10
No further disassembly is required to remove the BCM from the vehicle. From the trade feedback, we have received if you have followed these steps, and it has led you to the BCM, once a new BCM was installed, the shift lock system worked correctly.
At the time of printing, the price of a new BCM was approximately $300 AUD ($200 USD). But check with your parts supplier, as there are differences depending on the variant. These units seem to be repairable, but you will have to inquire with your preferred ECU repair business if it is economical to do so.
As stated earlier, the ix35 (Tucson) has the most requests for information about shift lock problems. However, other Hyundai and Kia models can cause trouble. There are different variants of the system like the Veloster FS, which have the same transmission but use the Smart Junction Box to earth (ground) the shift solenoid. La
ter models seem to have moved to a different design of knob with a button to release the shifter.
We hope that this article will make the diagnosis and repair of these vehicles faster and easier. However, there are many other issues that could impact this system. We have only covered the most common ones that we have heard of, and received feedback about successful repairs.
We would like to thank those VACC MotorTech subscribers that have shared their research, information and diagnostic experience about these common issues.
This should ensure that other VACC Members and VACC MotorTech subscribers can repair the shift locks in the ix35 (Tucson) correctly the first time.
For more diagnostic and repair information on the ix35 (Tucson), log on to VACC MotorTech or call VACC’s TechAdvisory Service.
We would like to thank the following for their assistance with this article.
- Brad from A&B Auto Electrical in Brookvale NSW, aabautoelectrical.com.au (02) 9939 4626
- Andrew from Cowan Motor Services in Mornington Victoria cowanmotorservices.business.site (03) 5975 0399
- Ryan from Precision Auto Electrics and Mechanical Repairs in Cranbourne, Victoria precision-auto-electrics.business.site (03) 5996 8625
Special thanks to the Victoria Automotive Chamber of Commerce (VACC) and MotorTech for permission to reprint this article!
