Start Control Unit (SCU) May Cause No Start Condition / No Key Release (TJ 7365)

START CONTROL UNIT (SCU) MAY CAUSE NO START CONDITION / NO KEY RELEASE

TECHNICAL SERVICE BULLETIN

VEHICLE TYPE

Type	Eng	Eng Desc	Sales	Body	Gear	Steer	Model Year	Plant	Chass. Range	Struc. Week Range
533	2007 -9999	0000261 -9999999	200637 -999999
542	2006 -9999	0000590 -9999999	200549 -999999
544	2004 -9999	0000295 -9999999	200339 -999999
545	2004 -9999	0000133 -9999999	200347 -999999

CSC

Code	Description
7B	Starting/Engine does not start/Engine does not turn/No clicking sound at start attempt
BE	Starting/Engine does not start/Engine does not turn/Unsure when/at all times
BJBO	Starting/Engine does not start/Unsure when/at all times
BO	Ignition lock/Key cannot be removed
IV	Text window and warning symbol/Text message
CC	Warning lights and chimes/Immobilizer indication/no indication

DTC

• CSC = Customer symptom code
• SCU = Start Control unit
• CEM = Central electronics Module
• DIM = Drivers information module
• TCM = Transmission Control unit
• SWM = Steering Wheel Module
• CAN = Controller Area Network
• SCL = Steering Column Lock

DESCRIPTION

Analyses of no crank / no start cases has shown that the SCU may be responsible for the following conditions:

1. +50 contact inside SCU sticking / not switching
2. Contact for solenoid activation sticking / not possible to remove the key
3. Key-in switch sticking / key removal and re-insertion not detected
4. Key transponder read problems / key validation not possible
5. Foreign debris in between contact points causing wrong key position.

PRODUCT MODIFICATION

Several improvements have been introduced since production start and only the latest status parts are available. New SCU introduced with new material in lower housing. Part numbers and chassis number introductions are listed below.

P/N 31300586: SCU with switch interlock (with solenoid). Used on cars with Automatic Transmission and all USA/Canadian variants

• TYPE/CHASSIS
• 533/174031
• 544/489453
• 545/528501

SERVICE

Follow the advice below based on Symptoms.

1. SYMPTOM 1.  No crank/No start, Key or Immobilizer DIM messages.

   Use the guided fault tracing in VIDA: Symptom Related Diagnostic Procedures/Cables and fuses/372 electrical distribution box, fuse box/Check the start system If the SCU is found to be faulty after following the fault tracing, replace the SCU.

2. SYMPTOM 2.  Radio continues to play with key out, chime active with key out, cannot lock car with remote (key in switch faults and wrong interpreted key positions).

   Use VIDA to read the key in switch at Diagnostics / Vehicle Communication / CEM / Parameters / Immo / Key-In-switch. If the SCU is found to be faulty after reading out values with VIDA replace the SCU.

3. SYMPTOM 3.  Key sticks or will not come out of SCU.

This fault symptom is only for vehicles with switch interlock (Used on cars with Automatic Transmission and all USA/CDN variants) To release the key, SCU pin B7 must have greater than 12 volts (30+) and SCU pin B8 must receive ground from CEM to activate internal solenoid in the SCU. The CEM sends the ground when gear position "P" (park) is received from TCM on CAN bus. If testing finds a faulty SCU, replace the SCU.

WARRANTY INFORMATION

SYMPTOM 1 Use One
36060-3 Check Key in switch	See VSTG
99231-2 Fault tracing no crank/no start using fault tracing.	0.4 hours
99414-2 Fault tracing CAN	1.1 hours
SYMPTOM 2
36060-3 Check Key in switch	0.1 hours
SYMPTOM 3
99400-2 Check power supply to key block solenoid	See VSTG
Use if applicable:
36001-2 Check/erase DTC's 36002-3 New Software	See VSTG
36020-2 SWM replace	See VSTG
33438-2 SCU replace	See VSTG
STG 37206-2 CEM replace	See VSTG
e VSTG 64108-2 SCL replace	See VSTG
37201-2 Fuse replace	See VSTG