Check engine codes

Tiny
FARR2007
  • MEMBER
  • 2001 CHEVROLET IMPALA
  • 3.8L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 258,000 MILES
I am dealing with these codes and need information on how to repair.

C1237
C1245
PO300
PO404
PO405
PO440
PO480
PO742
PO305
P1811
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Monday, April 24th, 2017 AT 1:13 PM

3 Replies

Tiny
STEVE W.
  • EXPERT
OOF, That's a list +

P0300 - Multiple Random Misfire
P0305 - Misfire Cylinder 5

P0404 - EGR performance - Out of Range
P0405 - EGR Sensor - Circuit voltage out of range Low
These two are EGR faults and could very easily cause the two misfire codes listed above them. So I won't cover the misfire repair unless the EGR faults are dealt with first.
The EGR needs to be tested with a scan tool so you can watch the position sensor and see if it is working. It is very common for these valves to get carbon built up in them which causes them to stick in one position. Sometimes you can clean the valve out with carb/choke cleaner and get it functioning again. The Exhaust Gas Recirculation valve lets some of the burned exhaust gas back into the engine to cool the temperatures inside the cylinders by diluting the fuel mix. Excess flow or flow at the wrong time from a stuck valve will give you misfires.

P0440 - EVAP system Large Leak
This one could be virtually anywhere in the EVAP system, bad gas cap, bad fill neck, damaged EVAP lines, Vent solenoid failure. Easiest way to test it is with a smoke machine. You apply smoke with the purge solenoid blocked and then look at the EVAP parts to see where the smoke is coming out. Should be readily apparent.

P0480 - Cooling fan relay control circuit 1 performance
This could be the relay itself or the wiring going to it. No real way to tell without using a scan tool to command the fans on/off and check the responses of the fans.

Both of the below are transmission codes, Trans needs to be tested and examined to determine the exact causes but the common ones are noted. Not a DIY repair.

P0742 - TCC (Torque Converter Clutch) Stuck in on position - When was the last time the transmission was serviced? This is 50/50 with dirty fluid or bad TCC solenoid valve as the cause.

P1811 - Max adaptive shift time - Very common code, Could be caused by the above code as well because the trans isn't shifting properly with the converter locked. Also can be caused by contaminated fluid or a bad solenoid.

These are both ABS codes.
C1237 - ABS code - High System Supply Voltage - This usually is related to a bad battery or alternator that is putting out excessive voltage. To test requires a simple volt meter connected across the battery, then the alternator while the engine is running. But it would be better to have the system tested for output voltage and any AC ripple current as it could be a bad diode letting AC spikes through that are causing the issue.

C1245 - ABS code - Low tire pressure detected (Not used on your vehicle, but the ABS unit does support it)
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Thursday, April 27th, 2017 AT 11:02 PM
Tiny
FARR2007
  • MEMBER
I am confused about the abs codes, as far as tranny goes fluid has t been changed ever that I know of
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Thursday, April 27th, 2017 AT 11:25 PM
Tiny
STEVE W.
  • EXPERT
The first ABS code is saying that the ABS unit is seeing a higher than specified voltage. That is easy to test with a voltmeter. If the alternator IS charging at a high voltage then it needs to be corrected. If it isn't then you have an issue in the ABS unit.

The second code probably isn't used on your vehicle, it would normally light up a light to tell you that you have a low tire, it counts the rpms of each tire and compares them. They should all rotate at very close to the same speed. However a low tire acts like a smaller tire so it has to turn faster to stay at the same speed the other tires are turning. That is how many tire pressure monitors work.

Well dirty fluid can cause the solenoids to stick. Dropping the pan, changing the fluid and filter may help, but a shop could put a scan tool on it and command the trans to shift in various ways and give you a better idea if it's a mechanical issue.
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Friday, April 28th, 2017 AT 2:04 AM

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