B2603 on Nissan

On 2013-2015 Altima sedans (L33 chassis), owners report walking up to the car, pressing the ignition button with a foot on the brake and the selector in Park, and getting nothing at all — no crank, no starter engagement — while an "I-Key Error" message appears in the combination meter. The complaint is usually intermittent at first and becomes more frequent over months. The root cause is not the Intelligent Key system despite the dash message. Nissan's shift-by-cable setup connects the console selector to a manual lever on top of the transaxle, and the transmission range switch (inhibition switch) mounted on that lever reports the actual mechanical gear position. The BCM cross-checks shift-position status before it will authorize the starter, and it sets B2603 (Shift Position Status) when it sees an invalid shift-position condition for 500 ms or more with the selector in P and the ignition ON. When the shift control cable is out of adjustment, the manual lever sits slightly off the Park detent even though the console lever feels fully in Park, so the range switch reports an ambiguous position and the BCM withholds start permission. Nissan bulletin NTB14-029b (classification EL14-013b, October 2, 2015), titled "ENGINE WILL NOT START (NO CRANK)," documents this pattern. Its confirming condition is DTC B2604 (PNP/Clutch Switch) stored past or present, and it states explicitly: "If the above condition should occur, the following DTCs may also be stored; B2603 (Shift Position Status), P0705 / P0706 (T/M Range Sensor A)." The bulletin applies to all 2013-2014 Altima sedans and to 2015 Altima sedans built before VIN breakpoints 1N4AL3AP(*)FN 878081 / May 22, 2015, 1N4AL3AP(*)FC 446505 / May 19, 2015, and 1N4BL3AP(*)FC 444362 / May 15, 2015. It covers both the QR25DE 2.5L four and the VQ35DE 3.5L V6, since the fault lives in the shift linkage and body electrical system rather than the engine. The bulletin also notes it does not apply to remote start issues.

2013-2015 Pathfinders (R52), including the 2014 Pathfinder Hybrid, suffer a documented no-crank condition in which the starter never engages when the ignition button is pressed and the combination meter displays "I-Key Error." Because the message points at the Intelligent Key system, owners and shops frequently spend money on fobs, fob batteries, key antennas and even BCMs before the real fault is found. The defect is a disagreement between two independent reports of where the transmission actually is. The BCM monitors shift-position status; the TCM reports the transmission range switch state from the switch on top of the CVT. B2603 sets when, with the ignition ON and the selector in P, the BCM sees an implausible shift-position condition persisting for 500 ms or more. Technicians describing this code on the R52 note it sets when the input from the TCM and the CVT shifter are both reading zero volts — an impossible combination if the car is genuinely in Park. With that mismatch present the BCM will not authorize a start, and the generic I-Key fault message is raised because the start-authorization chain failed. The documented cause on this platform is shift control cable misadjustment, covered by Nissan bulletin NTB14-029b (EL14-013b, October 2, 2015). Its applied-vehicle list includes 2013-2015 Pathfinder (R52) and 2014 Pathfinder Hybrid (R52) — all 2013-2014 Pathfinders, and 2015 Pathfinders built before VIN 5N1AR2M(*)(*)FC 674573 / May 19, 2015. The bulletin's confirming code is B2604 (PNP/Clutch Switch) stored past or present, and it states that B2603 (Shift Position Status) and P0705/P0706 (T/M Range Sensor A) may also be stored. A misadjusted cable leaves the manual lever slightly off the Park detent, so the range switch reads an ambiguous position.

2014-2015 Rogues on the T32 platform develop a no-crank start failure in which pressing the ignition button with the brake applied and the selector in Park produces silence — no starter engagement — and the combination meter shows an "I-Key Error" message. Nissan bulletin NTB14-029b (EL14-013b, October 2, 2015) lists all 2014 Rogues and 2015 Rogues built before VIN 5N1AT2M(*)(*)FC 879622 / May 19, 2015, and carries an explicit note that it does not apply to the Rogue Select (S35), which uses different hardware. The mechanism is a shift-position disagreement, not a key or starter fault. The console selector pulls a shift control cable to a manual lever on top of the CVT, and the transmission range switch (inhibition switch) on that lever reports which gear the transaxle is mechanically in. Before energising the starter the BCM requires a valid shift-position status. When the cable is misadjusted, the manual lever rests just off the Park detent while the console lever feels perfectly seated, so the range switch output is ambiguous, and the BCM stores B2603 (Shift Position Status) after seeing the invalid condition for 500 ms or more with the ignition ON. The bulletin's confirming code is B2604 (PNP/Clutch Switch), and it states B2603 along with P0705 / P0706 (T/M Range Sensor A) may also be stored. Because the Rogue's hardware differs from the Altima and Pathfinder, Nissan specifies a lower cable nut torque and a longer labor time for this model. The same era of Rogue has separate, unrelated shifter trouble: NHTSA recall 15V-775 covered roughly 33,880 2015 Rogues built February 10 to May 13, 2015, for a shift selector knob with uneven spring pressure that allowed shifting out of Park without the brake pedal depressed, a rollaway risk. That recall is a knob-and-spring defect, not the B2603 cable adjustment, but a Rogue with odd shifter behaviour is worth checking against both.

A recurring owner complaint on newer Sentras involves weak factory batteries, hard starting, no-start conditions, or stalling/rough restart behavior associated with the idle stop/start system. The problem often appears early in ownership and may be aggravated by short-trip driving or battery state-of-charge issues. In some cases, owners report multiple jump-starts or battery replacement within the first few years.