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  #1  
Old June 16th, 2014, 03:19 PM
Roverlab
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Trevor Griffiths
85 110, 92 110, 92 RR, 06 LR3
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97 nas 90

Hi all!
I have an unusual problem with this 90 and wanted to run it by you:

The 90 came in with the Check Engine light on.
Connecting Autologic or a generic scan tool to the diag port results in no communication with the engine ECU.
Scan tools work on other Rovers with no issues.
Began checking continuity of the 6 wires in the diag port: 2 grounds, purple battery power, white/pink to engine ecu, white/light green to ABS ECU.
All had nearly identical normal readings.
Substituted know good ECU, same concern.
Fit this car's ECU into another GEMS and I can read the codes P1607 and P1617. Cleared the faults, refit into this 90 and the CEL is out. Still can't read codes.
Here's where it gets interesting:
The last wire is orange/light green going to alarm unit. Reading through the RAVE, there is reference to the alarm unit having some effect on the Check Engine light as part of it's function to Immobilise the car from starting ie: the CEL wont illuminate if the Immobiliser is in effect.
The owner had someone instal a toggle switch in-line to the green wire that supplies power to the immob unit through fuse 17. If I flip the switch, the Rover wont crank, and I would assume doesn't have spark or fuel pulse. If I flip it back, the engine will start. In either position, I can't communicate with the engine ECU.
Currently, the CEL is off after having been cleared in another Rover and re-fitted to the original, the car runs, but does not communicate.
I don't know if the interrupting the power to the immobiliser has managed to get the ECU and Immob out of synch, but if they were , I would think the car wouldn't start.
I'm stumped, looking for fresh ideas....
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  #2  
Old June 17th, 2014, 07:39 AM
M.A.R.S.
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Drew
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when you where checking the white/pink wire to the engine ecu and the white/green wire to the abs ecu did you check that they go to the other ecu's. both the white/pink wire and white/green wire need to connected to both the abs and engine ecu.

have you pulled faults from the abs ecu? i have seen on other rovers when the abs ecu has faults t4 won't pull codes from the engine ecu.

the immobilizer should have its own wire to the obd2 port have you scanned that? why was the toggle switch installed?

sounds like you have already checked but power and ground at obd2 port.
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  #3  
Old June 17th, 2014, 08:28 AM
Roverlab
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Trevor Griffiths
85 110, 92 110, 92 RR, 06 LR3
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Drew, thanks for the reply.
w/k and w/g have continuity from the aldl to both the abs and gems ecu's and the same voltages with ignition on.
ABS ECU shows no faults, but loses communication within about 1 minute after entering that screen.
toggle switch was a security measure, installed before I ever worked on the car and hadn't been a problem as far as I know.
I can communicate with security through the scan tool.
Scan tool powers up, so I'd say the power and ground are sound. I had added an additional ground at one pint to ensure that wasn't an issue. They ground through the big gang on the fire wall- cleaned and refitted but were in good condition to start with.
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  #4  
Old June 17th, 2014, 08:52 AM
M.A.R.S.
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Drew
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I have never tried reading voltage on w/k and w/g what are they?

what about the obd2 port its self. I have seen the terminals inside them become spread and not make good connection with the scan tool. if that looks good then I would guess that there is a problem on one of those wires to the eng/abs ecu. I would think that it would show up on a resistance test but maybe not. Do you have a parts d1 truck? cut a obd 2 port out and add power and ground to it then splice in the two wire to engine ecu for a test.
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  #5  
Old June 17th, 2014, 11:01 AM
Roverlab
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Trevor Griffiths
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Correction, I did not apply an additional ground at "one pint". Should have been 1 point. The pints came later when I grew tired of scratching my head and saying wtf.
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  #6  
Old June 17th, 2014, 03:25 PM
Roverlab
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Trevor Griffiths
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Started over this morning. Still have the same results:
no comm to the GEMS.
Confirm continuity and voltages on the 6 wires at the obd2.
white pink at the ABS and GEMS with engine running voltage of 12.8,
white light green at both ABS and GEMS 12.4v
orange light green to security also 12.8v
purple 13.6v
Confirmed voltages using 2 grounds in obd2 as well as a seperate chassis point
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  #7  
Old June 17th, 2014, 03:27 PM
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Ron
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mine had the same issue, by disconnecting the abs ecu I was able to communicate.
and clear codes, I then reconnected the abs ecu and go about my business.....
: )
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  #8  
Old June 17th, 2014, 04:04 PM
Roverlab
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Trevor Griffiths
85 110, 92 110, 92 RR, 06 LR3
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I found it. Going to put the car back together first and keep y'all in suspense...... I'm sure everyone is on the edge of their seat for this one. Now I have to figure how to bill for my considerable time.....
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  #9  
Old June 18th, 2014, 07:09 AM
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Drew
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what did you find
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  #10  
Old June 18th, 2014, 09:49 AM
Roverlab
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Trevor Griffiths
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I found a lot of resistance in the aftermarket switch that was on the power side of the security unit. removed that and found that I could now enter the GEMS. Great, so I thought.
As I was working across the car and putting things back together, I realised I had proved this with the ABS ecu not connected.
Reconnect and the inability to enter GEMS returned. So, at least now I know which system is creating an issue. Substituted another ABS from another 97 with the same symptom.
And that's where I am in the driveway, as the shop is full of 109 and 110.
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  #11  
Old June 18th, 2014, 11:10 AM
Roverlab
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Trevor Griffiths
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Done. Bad ground to the ABS ECU.
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