P26AB: Early 2013 Ram coolant-bypass warning with a PCM calibration remedy

The bulletin provides a software branch

P26AB is described as engine coolant bypass valve stuck in this early Ram application. Chrysler documented an illuminated malfunction indicator and directed a PCM software update for the specified vehicles. The repair procedure does not call for replacing the bypass valve. That gives the workshop a concrete calibration check before ordering hardware, while leaving other possible causes to the normal diagnostic procedure.

Confirm the narrow production scope

Record the engine, build date, full scan and installed PCM software. The 2013 model year alone is insufficient: the bulletin restricts this case to the 3.6 L engine and an early production cutoff. It instructs technicians to verify engine-system operation and address other codes before applying the update. Temperature warnings, coolant loss or additional symptoms should therefore be included on the repair order rather than attributed automatically to the calibration.

What to request after programming

The historical procedure uses the manufacturer programming process with controlled battery support, clears codes generated by programming and records the authorized modification on a label. For a vehicle repaired years later, the workshop should identify the current applicable calibration rather than install an obsolete file simply because its bulletin number matches. Ask for the before-and-after software identification and whether P26AB returns under normal operation. A persistent fault after a correctly completed update requires the vehicle’s bypass-valve diagnosis; this short bulletin supplies no electrical pin tests or mechanical acceptance limits.

Source and applicability

Chrysler bulletin 18-017-13, April 2013: 2013 Ram 1500 DS with 3.6 L ERB engine, built before March 20, 2013.

Manufacturer bulletin, page 1 · Manufacturer bulletin, page 2