BillyD
04-04-2004, 20:55
My SES (Service Engine Soon) light came on the other day while driving approximately 65-70 mph up a slight grade unloaded.
10-15 seconds after the SES light came on there was a significant loss of power. Depressing the accelerator pedal to maintain speed caused the transmission to down shift at least one gear.
As road speed continued to drop, even though the accelerator pedal remained depressed, the transmission continued to down shift until, at one point, maximum speed that the truck could maintain was approximately 15 mph.
I pulled over to check things out. Stopping and starting the truck had no effect on the SES light; however, the truck would idle fine. All guages were within normal ranges.
I decided to keep going and found that if I kept the engine speed below 1900 RPM and lifted momentarily on the accelerator just as 1900 RPM was reached, the transmission would upshift through the gears.
If I attempted to exceed 1900 RPMs, the engine would "stumbled" and the transmission would successively downshift until the accelerator pedal was released. I pulled over, put the truck in Park, returned the gear selector back to drive and was able to continue so long as I kept below 1900 RPMs.
After the truck had been turned off for a couple of hours, the SES light was gone and the truck again drove normally. Just to be safe, I replaced the NSBU switch with the Tan two-connector version. After three days, however, the SES light came back on and the same symptoms reappeared (power loss and down shifting).
A search on "SES" did not yield any relevant results; hence, this post. The truck is in the dealer now, but haven't heard whether they've recovered any error codes.
Any suggestions would be appreciated.
In the interest of completeness, I should point out two other items. At 74,000 miles I had the ECM and alternator replaced under warranty. The other item is that the cruise control occassionally cuts out when attempting to use the Accelerate slide switch (no difference with new ECM).
If the dealer comes up with anything, I will post the findings here in case anyone else experiences a similar problem.
Thanks.
BillyD
10-15 seconds after the SES light came on there was a significant loss of power. Depressing the accelerator pedal to maintain speed caused the transmission to down shift at least one gear.
As road speed continued to drop, even though the accelerator pedal remained depressed, the transmission continued to down shift until, at one point, maximum speed that the truck could maintain was approximately 15 mph.
I pulled over to check things out. Stopping and starting the truck had no effect on the SES light; however, the truck would idle fine. All guages were within normal ranges.
I decided to keep going and found that if I kept the engine speed below 1900 RPM and lifted momentarily on the accelerator just as 1900 RPM was reached, the transmission would upshift through the gears.
If I attempted to exceed 1900 RPMs, the engine would "stumbled" and the transmission would successively downshift until the accelerator pedal was released. I pulled over, put the truck in Park, returned the gear selector back to drive and was able to continue so long as I kept below 1900 RPMs.
After the truck had been turned off for a couple of hours, the SES light was gone and the truck again drove normally. Just to be safe, I replaced the NSBU switch with the Tan two-connector version. After three days, however, the SES light came back on and the same symptoms reappeared (power loss and down shifting).
A search on "SES" did not yield any relevant results; hence, this post. The truck is in the dealer now, but haven't heard whether they've recovered any error codes.
Any suggestions would be appreciated.
In the interest of completeness, I should point out two other items. At 74,000 miles I had the ECM and alternator replaced under warranty. The other item is that the cruise control occassionally cuts out when attempting to use the Accelerate slide switch (no difference with new ECM).
If the dealer comes up with anything, I will post the findings here in case anyone else experiences a similar problem.
Thanks.
BillyD