Hello, I must add more information. THis code is often set because the battery went dead and you tried to start it. There is a calibration update to correct this and it will not require a new ECM. See you dealer for the calibration update.
Below is the bulletin that outlines this code and I have dozens of this update and never replaced a ECM for this.
#PIP4403: Control Module Ignition On Timer Performance DTC P2610 - keywords 6.6 cal calibration ECM engine LBZ LLY MIL replace replacement - (May 1, 2008)
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
A dealer may encounter a customer complaint of a check engine light (SES light ON) and a P2610 DTC may be stored in the ECM. This DTC may set intermittently after a reflash of certain modules such as the transmission control module (TCM), or glow plug control module (GPCM). Additionally, any loss of battery voltage to the ECM while the ignition is ON, can also cause a P2610 to set.
If a P2610 has been verified do not replace the ECM. Perform the following steps when encountering a P2610.
Turn the IGNITION OFF for 90 seconds. Unplug both the engine control module (ECM) connectors for 90 seconds. After 90 seconds has passed, re-install the ECM connectors. With the ignition on use the Tech2 and clear all codes in the ECM. This procedure should prevent future sets of the P2610. For 2006 and certain 2007 model vehicles, there may also be a calibration update available which addresses P2610 false sets.