Summary:

2004 Prius gen2/XW20, 157k mi sudden behavioral change: revving at unusual times, seems to be relying on ICE, possibly causing hesitation when accelerating from stop or up steep hills. Surprising enough to turn back on a roadtrip.

Codes: P3000, C1310, C1259, intermittent P0130

Looking to diagnose and also asses risk of safety or damage in continuing to drive with current problems including for hours at a time at highway speeds.

Context:

I’ve owned this Prius for 3 years, and do much of my own maintenance when possible.

I hit the road yesterday for a 6-hour interstate drive. About an hour in, while holding the throttle steady, RPMs rise, hold for a few seconds, fall, rise for a few seconds, fall- for 5 or so rounds. But no change in acceleration or power. I exit, come to a complete stop, It’s night and the lights are on but nothing else, and ICE is running steady. From a stop, I give it throttle and there’s a pause before I get power, then the same sort of revving under consistent throttle but this time results in acceleration/power. After some research, I head back home. I noticed I was hardly using the electric motor- the ICE was doing all the work and pouring energy into the hybrid battery as well. Only while braking downhill on the interstate did braking seem to be recharging the battery. I felt like maybe the engine was louder than usual but it just felt loud in the car in general. Didn’t notice the hybrid battery fan come on.

Of note: recently had a wheel bearing changed- front passenger. When I got it back, the VSC and (!) lights were on- the one with the tire not the red triangle of death. I took it back and they said nothing was wrong but didn’t reset the lights (new favorite mechanic). Those lights have remained on and were on last night. Cruise control wouldn’t work either. Speed sensor? But today a diagnostic said all the sensors were working fine and showed consistent speeds.

Pulled these codes today:

• P3000– yikes
• C1310
• C1259
• intermittent P0130

Also had some trouble under high torque up a steep hill- the same sort of pause before getting power.

AND I’ve had this problem since last summer where under high torque, usually uphill on an interstate or highway, I’ll get a stutter- the same sort of loss of power but like it’s stammering. If I let up a bit, I regain power. I cleaned the throttle body with no change.

AND I am aware that my hybrid battery is wearing out. I have a prolong battery charger/discharger which I just used and it was up to 235v when I unplugged. (any one over here have thoughts about these? PriusChat has been all about em in the past)

Obvious request is for help with diagnosis(es). But also, what about driving it like this? What about driving like this on the interstate? Is there a risk of long term damage?