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Pete, Automotive Mechanic
Category: Transmissions
Satisfied Customers: 27814
Experience:  GM and Mercedes vehicle technician.17 years experience.
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2005 Isuzu NPR 5.2 L diesel. has a shifting problem with

Customer Question

Hi 2005 Isuzu NPR 5.2 L diesel. has a shifting problem with throttle is won't shift, let off gas and it shifts, P1839 and P0670, replaced all glow plugs and rebuilt tranny and flushed all lines and replaced torque converter. worked fine for 2 days then started doing it again
JA: Sometimes things that you think will be really complicated end up being easy to fix with a Isuzu. The Mechanic I'm going to connect you with knows all the tricks and shortcuts. Are you hoping to fix this yourself?
Customer: Im a mechanic, just very unfamiliar with this vehicle
JA: Is there anything else important you think the Mechanic should know about your Isuzu?
Customer: All the same codes were present before trans repair and glow plug replacement, just a odd observation, charged the vehicle up completely before it left and trans shifted beautiful for 2 days then started same symptoms after what could be low voltage. Haven't checked the voltage or Alt yet as truck is not here yet
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Transmissions
Expert:  Pete replied 1 year ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.

This may be an issue with the transmission valve body itself as this is a known issue in some cases for a fault like this here.If you can clear out the codes then operate the vehicle as best or much as possible until the fault occurs and see which code sets first here and let me know this will help.

Thanks Pete

Customer: replied 1 year ago.
Existing P0670, won't erase, and reoccurring P0700 And a P1839 that I can't find a definition for
Expert:  Pete replied 1 year ago.

The code P0670 looks to be a fault with the glow plug circuit,glow plug or glow plug controller/ecu itself.This wont cause a shifting issue here but can cause start up faults and needs diagnosed to locate and repair the issue here.

The code P1839 is a fault with the transmission fluid temp sensor.This can be a faulty temp sensor or wiring inside the transmission to the sensor needing repaired and can cause shifting or other transmission issues.This will have to be checked into/tested further as well to pinpoint the cause and then repaired from there.I suspect the temp sensor is at fault needing replaced as this is most common.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete