Solved my code 26 problem
Discussion
Hi all, I have had a code 26 problem for nearly 18 months now. The fault was intermittent and would only appear during urban / low load condition driving. It would never appear whilst travelling down the motorway etc.
The solution was to replace the charcoal cannister solenoid. I had previously checked this and it was working (although with hindsight it was a little weak) so I started looking at other things.
My advice from all of this for anybody with a code 26 fault is, with the ignition on, short across the two pins on the ALDL connector that you use to read the fault codes. This should activate all the solenoids and relays associated with the fault code. Any that are not activated or are fairly weak are likely to be to blame. If the wiring is suspect this technique can also be useful because you can leave the pins shorted and wiggle all wiring whilst holding each relay and solenoid in turn. If any switch on and off then there it is likely that there is a problem with the wiring.
I realise that code 26 can be any one of 9 different things but this technique, which is stated in the engine management manual, applies. The symptoms of the fault can help narrow down which component is likely to be at fault. For example my fault was only apparent at low load and overrun conditions and it makes sense that the ECU tells the charcoal cannister to purge the fuel vapours under these conditions. Another example would be that if the fault occurred at high throttle settings when the engine is above 82 degrees C then the wastegate solenoid would be worthwhile looking at.
I hope that this is of some use to people as I know how frustrating it is to have this particular problem. It is well worth checking the individual compoinents before changing the ECU itself.
Danny Tattersall '93 SE Highwing negative code 26 problem.
The solution was to replace the charcoal cannister solenoid. I had previously checked this and it was working (although with hindsight it was a little weak) so I started looking at other things.
My advice from all of this for anybody with a code 26 fault is, with the ignition on, short across the two pins on the ALDL connector that you use to read the fault codes. This should activate all the solenoids and relays associated with the fault code. Any that are not activated or are fairly weak are likely to be to blame. If the wiring is suspect this technique can also be useful because you can leave the pins shorted and wiggle all wiring whilst holding each relay and solenoid in turn. If any switch on and off then there it is likely that there is a problem with the wiring.
I realise that code 26 can be any one of 9 different things but this technique, which is stated in the engine management manual, applies. The symptoms of the fault can help narrow down which component is likely to be at fault. For example my fault was only apparent at low load and overrun conditions and it makes sense that the ECU tells the charcoal cannister to purge the fuel vapours under these conditions. Another example would be that if the fault occurred at high throttle settings when the engine is above 82 degrees C then the wastegate solenoid would be worthwhile looking at.
I hope that this is of some use to people as I know how frustrating it is to have this particular problem. It is well worth checking the individual compoinents before changing the ECU itself.
Danny Tattersall '93 SE Highwing negative code 26 problem.
danny tattersall said:
My advice from all of this for anybody with a code 26 fault is, with the ignition on, short across the two pins on the ALDL connector that you use to read the fault codes. This should activate all the solenoids and relays associated with the fault code. Any that are not activated or are fairly weak are likely to be to blame. If the wiring is suspect this technique can also be useful because you can leave the pins shorted and wiggle all wiring whilst holding each relay and solenoid in turn. If any switch on and off then there it is likely that there is a problem with the wiring.
Danny. I have a code 26 at the moment and would like to try what you have recommended above, but I know as much about electronics as I do nuclear fission. If you don't mind, could you expand on the above paragraph detailing what the equipment needed and process is please?
What confuses me on my problem is that I think we isolated the issue to the bottom bank of 4 solenoids in the area in the boot (using FreeScan at Donnington). If I get the Check Engine light appear my boost is restricted, so I pull over and pull each of these 4 solenoids out. I then have 30 minutes or so of trouble free hooning. Does this help with diagnosis at all?
Many thanks in advance.
Jason '89 SE
Jason,
I take it that you mean the bottom bank of relays (not solenoids). Are you sure that the fault only resets when you pull those four out and replace them or will it reset and give you the same amount of 'hooning' time if you simply switch off and then switch back on the ignition. If the switching off and then on of the ignition does not have the same affect as pulling the relays then I would suggest that the problem lies in a faulty relay or wiring to the relays. Try shorting the bottom two right hand side connections on the ALDL plug to put the ECU into code reading mode and check that all the relays are activated. For your information, only the right hand 3 relays are associated with the code 26 as the one on the far left is the starter motor solenoid relay. It may be worthwhile undoing the two screws that secure the relay holder to the bulkhead and checking that each of the terminals to the relays are positively located.
Hope you have some joy with this. If you need any more info let me know.
Danny
I take it that you mean the bottom bank of relays (not solenoids). Are you sure that the fault only resets when you pull those four out and replace them or will it reset and give you the same amount of 'hooning' time if you simply switch off and then switch back on the ignition. If the switching off and then on of the ignition does not have the same affect as pulling the relays then I would suggest that the problem lies in a faulty relay or wiring to the relays. Try shorting the bottom two right hand side connections on the ALDL plug to put the ECU into code reading mode and check that all the relays are activated. For your information, only the right hand 3 relays are associated with the code 26 as the one on the far left is the starter motor solenoid relay. It may be worthwhile undoing the two screws that secure the relay holder to the bulkhead and checking that each of the terminals to the relays are positively located.
Hope you have some joy with this. If you need any more info let me know.
Danny
Danny,
Many thanks for the reply.
Yes, you're right - the big black things with 3 or 4 pins.
No, if I come to a standstill and turn the engine off and back on again, the time the light takes to come back on varies, but is significantly shorter. Sometimes it can be instantaneous, other times it can be when I start moving off.
This is where I need a little nursing really. How do I go about doing this bit?
Thanks again for your help.
Jason.
>> Edited by jesprit on Friday 15th April 15:18
Many thanks for the reply.
danny tattersall said:
I take it that you mean the bottom bank of relays (not solenoids)
Yes, you're right - the big black things with 3 or 4 pins. danny tattersall said:
Are you sure that the fault only resets when you pull those four out and replace them or will it reset and give you the same amount of 'hooning' time if you simply switch off and then switch back on the ignition.
No, if I come to a standstill and turn the engine off and back on again, the time the light takes to come back on varies, but is significantly shorter. Sometimes it can be instantaneous, other times it can be when I start moving off.
danny tattersall said:
and check that all the relays are activated.
This is where I need a little nursing really. How do I go about doing this bit?
Thanks again for your help.
Jason.
>> Edited by jesprit on Friday 15th April 15:18
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