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Not my car ... but my buddy’s 2011 CRZ with 90k miles finally got the death of IPU fan message.
Before the IMA light turns on, there was some strange noise from the trunk area. Within a couple of weeks, the IMA light turned on. I was 95% sure that’s the IPU fan needing to be replaced so my buddy ordered it.
According to multiple threads, it is possible to have the IPU fan covered under the hybrid warranty (15 years / 150k miles warranty in California) and most cases owners only had to pay about $100. My buddy doesn’t want to go through hoop and loops / Honda Headquarter to get it fixed under warranty. He can’t afford the down time of his car.
Symptoms:
- The engine is turned on by the conventional starter by the 12v battery and not the synchronous induction motor by hybrid battery. (Engine Start like a non-hybrid car).
- No hybrid / IMA assist at any RPM.
- 12v battery reads only 10.7v at idling and 12.7v at 2-3k rpm. It’s considered low but the car seems to run fine but battery is draining.
- Turning off the main breaker of the main hybrid battery doesn’t seem to change anything.
- Fuse #53 is burned under steering wheel (you may or may not have this fuse burned)
Tip:
- Assuming the 12v battery is healthy, wait 5-6 seconds at the “On” position before starting the engine. If you turn the key from off to start position too quickly, the conventional starter will not crank over.
Here is a screenshot of the codes:
————————————————————-
Update (9/14/2021):
Quote from Facebook from Richie Poff:
“ … any 06 or newer hybrid Honda’s has the same internals for the IPU fan assembly. The only thing different is the housing the assembly sits in.”
————————————————————-
Update (2/7/2020):
New IPU fan part number:
Installation/Removal:
1. Take the spare and foam pieces out
2. Access the right rear plastic panel partially.
3. Loosen the three 10mm bolts on the IPU fan
4. Loosen plastic exhaust tube coming out of the hybrid battery to give you room to to wiggle the IPU fan around. Unplug the IPU fan harness
5. Loosen all the plastic clips around the IPU fans (7-9clips and be careful not to bend those clips too hard). Patience is key.
6. Take out the IPU fan without the exhaust tube
Comparison of old and new to make sure they match:
Old on the left and new on the right:
7. Put in the new fan and connect the harness
8. Replace the burned #53 IMA fuse located near the driver’s knee area (I forgot to replace mine and thought my DC-DC converter was not working). This fuse was burned out to protect the DC-DC converter to operate without a working IPU fan.
9. Disconnect the 12v battery and wait half a minute. I open my doors to discharge any residual power.
10. Reconnect the battery and switch the key to “ON” position (Not starting). Leave it there for at least 10-15 seconds until the system checks itself.
11. Turn on the car and all the messages should be gone. (Both my P1634 and P1448 are gone)
Comments:
If you ever get any of those error codes related to IPU fan or charging system. I highly recommend NOT to drive your car around because you can loose power steering/ABS, risking others on the streets as well as yourself. My buddy was lucky to drive home without power steering. The car pretty much ran really rough without proper 12v charging voltage.
Yes, the hybrid system components should be covered by warranty in CA but my buddy doesn’t want to go thru dealer and do all the explanations.
The IPU fan was 9 years old and the car had less than 90k miles. The fan did make some weird noise
I hope this write up helps and I am not responsible for any damages caused when you replace the fan yourself. Do it at your own risk.
Before the IMA light turns on, there was some strange noise from the trunk area. Within a couple of weeks, the IMA light turned on. I was 95% sure that’s the IPU fan needing to be replaced so my buddy ordered it.
According to multiple threads, it is possible to have the IPU fan covered under the hybrid warranty (15 years / 150k miles warranty in California) and most cases owners only had to pay about $100. My buddy doesn’t want to go through hoop and loops / Honda Headquarter to get it fixed under warranty. He can’t afford the down time of his car.
Symptoms:
- The engine is turned on by the conventional starter by the 12v battery and not the synchronous induction motor by hybrid battery. (Engine Start like a non-hybrid car).
- No hybrid / IMA assist at any RPM.
- 12v battery reads only 10.7v at idling and 12.7v at 2-3k rpm. It’s considered low but the car seems to run fine but battery is draining.
- Turning off the main breaker of the main hybrid battery doesn’t seem to change anything.
- Fuse #53 is burned under steering wheel (you may or may not have this fuse burned)
Tip:
- Assuming the 12v battery is healthy, wait 5-6 seconds at the “On” position before starting the engine. If you turn the key from off to start position too quickly, the conventional starter will not crank over.
Here is a screenshot of the codes:

————————————————————-
Update (9/14/2021):
Quote from Facebook from Richie Poff:
“ … any 06 or newer hybrid Honda’s has the same internals for the IPU fan assembly. The only thing different is the housing the assembly sits in.”
————————————————————-
Update (2/7/2020):
New IPU fan part number:
- 1J810-RTW-003
- A 15A Low-profile Mini fuse
Installation/Removal:
1. Take the spare and foam pieces out
2. Access the right rear plastic panel partially.

3. Loosen the three 10mm bolts on the IPU fan

4. Loosen plastic exhaust tube coming out of the hybrid battery to give you room to to wiggle the IPU fan around. Unplug the IPU fan harness

5. Loosen all the plastic clips around the IPU fans (7-9clips and be careful not to bend those clips too hard). Patience is key.
6. Take out the IPU fan without the exhaust tube

Comparison of old and new to make sure they match:
Old on the left and new on the right:

7. Put in the new fan and connect the harness
8. Replace the burned #53 IMA fuse located near the driver’s knee area (I forgot to replace mine and thought my DC-DC converter was not working). This fuse was burned out to protect the DC-DC converter to operate without a working IPU fan.
9. Disconnect the 12v battery and wait half a minute. I open my doors to discharge any residual power.
10. Reconnect the battery and switch the key to “ON” position (Not starting). Leave it there for at least 10-15 seconds until the system checks itself.
11. Turn on the car and all the messages should be gone. (Both my P1634 and P1448 are gone)
Comments:
If you ever get any of those error codes related to IPU fan or charging system. I highly recommend NOT to drive your car around because you can loose power steering/ABS, risking others on the streets as well as yourself. My buddy was lucky to drive home without power steering. The car pretty much ran really rough without proper 12v charging voltage.
Yes, the hybrid system components should be covered by warranty in CA but my buddy doesn’t want to go thru dealer and do all the explanations.
The IPU fan was 9 years old and the car had less than 90k miles. The fan did make some weird noise
I hope this write up helps and I am not responsible for any damages caused when you replace the fan yourself. Do it at your own risk.