help! engine code po481 camaro ss

**mikeyblue01** · 02-07-2012, 07:53 PM

Hi guys. just looking for a little help with an issue im having

Car...1998 camaro ss, 5.7 ls1, all stock

Problem... Engine code po481, chilton manual reads as cooling fan relay 2 and 3 control circuit

What I have done.... tried to reset code, came back on instantly, replaced all cooling fan relays, checked all fuses, hard wired both fans to test fan motors, turned on ac and the left fan turned on as it should (left, if you were looking at the engine from the front of the car), I have yet to see the right fan turn on during operation, car does not overheat, at full temp the needle bearly gets past the quarter mark

any input would be appriciated, thx, mike b

**Too Fast** · 02-12-2012, 05:12 AM

Are you sure you checked/replaced the correct relays? There are 2 fuses for the fans. You've proven out they are both good, since if either one were bad, there would be no fan action. 481 is the code for high speed fan operation, needed for high AC high-side pressure relief or when then engine is over ~228*. The code won't set unless there is a short to ground (unlikely), short to voltage (unlikely) or an open ciruit (likely). Also, the PCM could have an internal failure for this circuit.

Do you have access to a scan tool w/bi-directional control? That way you can command the high speed fan on with it, to check all the wiring. You say the fans work if you jump them, so I would look for a bad circuit in the high-speed control, especially the dark-blue wire to the relays.

The fans work on low speed like this:
Power for low operation is fed thru the cooling fan relay #1, commanded on by the PCM from the dark green wire, and then the light blue wire at the fan will have B+ voltage. The grey wire at that left fan is the ground, and it grounds after going thru cooling fan relay (CFR) #3 and thru the right cooling fan. The right fan acts as a resistor, limiting current flow thru the fans. Both fans should be on low speed, not one.

For high speed, the PCM commands CFR #2 and#3, thereby giving each fan their own ground, so they can operate full power.

I bet your problem is in the dark blue wires going to the high-speed relays (#2 & #3). IF that's ok, then check for voltage at the white wire to the right fan when there is a need for high speed fan operation, which you probably don't have, and find out where it is lost.

**mikeyblue01** · 02-13-2012, 09:07 AM

Thank you for the reply, I verified correct relays and no open fuses, wish it was that simple, I'm about to start checking the wires I'll reply with the problem when I find it, thanks again

**Too Fast** · 02-13-2012, 02:03 PM

Are you sure you only have one fan working? The wiring diagram is for the fans as viewed from the drivers seat, that's how I'll refer to them. If only the left fan works, then you have a problem with the grey wire being grounded somewhere before it makes it to relay #3.

A bi-directional scanner would really help to diag this problem.

With cool weather like this, you really only need low speed operation, I don't recall the high speed fan operation unless I'm stopped with the AC on, idling, in the summer. The high AC pressure needs a high flow across the condensor. Otherwise, unless you have some over-heating condition, high speed isn't necessary.

Good luck.