C1140 Code; ESP/clockspring/steering Angle Sensor Problem. Same ...

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Australian Fresh on the success of my P0410 fix (secondary air injection) which turned out to be the K40 (I’m dead chuffed after some of the horror stories I’ve read), I thought I might tackle my longest standing code. I have researched my C1140 to death. I found several posts on this forum, more on the R171 chat, and others on Benzworld.org, particularly the ML section (relevance is debateable). Anyway, I have a C1140 error code, but interestingly NO dash warning light (which all the posts I’ve seen list as a symptom). My investigations list the following as possible faults: 1. Steering angle sensor; open-circuit/short-circuit. Initialisation. This is from my Carsoft, which has proved somewhat unreliable in the past, hence my query to Jeff, the Oracle, who contributed some of the following, 2. B34 ESP brake pressure sensor – electrical fault; 3. Steering angle sensor N49 faulty (unlikely, would cause dash warning light......surely?); 4. Play in steering column causes steering angle sensor to lose memory (unlikely, see below); 5. Wheel alignment; (I don’t think this is a problem – I had the steering alignment checked/adjusted just after I bought the car but before my first Carsoft scan (so I can’t confirm the code was there previously) but the car steers tightly & dead straight and the steering wheel is on the right splines, etc). The code won’t reset – it doesn’t need engine starting or anything like that to come back; it just doesn’t go away. I was so excited when I read about a well-known wiring problem related to a loom being too short (no pun intended), but that seems to be limited to the R171, not the R170. Addressing the above possible faults, I think the first is most likely. I’ve read one post that said no-one on that forum had reported a faulty brake pressure sensor so far, and the others, I would think, would generate a dash warning light. I have had the steering wheel off, only to find the steering angle sensor (clockspring) is a plug-in unit. Obviously the wiring exits the steering column somewhere but I didn’t have time to dismantle the lower dash to find out where. I know the ESP works because the triangle on the dash flashes appropriately (and I’m still facing the right way). I don’t know if the BAS is working (or if it’s related) – but again, no dash warning light. If it is a wiring fault (short) on the steering angle sensor then I’m thinking it can’t be the 12v supplies – permanent and switched - as it would bIow a fuse, it can’t be on the earth wire (well, it wouldn’t make any difference) so it must be on the signal wire to the control unit. I would doubt the steering angle sensor is faulty (because I would think it would cause a dash warning light) but it would be nice to check it. As it’s a plug in unit, and the connector to the brake control module is a multi function plug-in thingy, how do I measure the voltage generated by the steering angle sensor (how do I get the test lead in)? If it’s an open circuit, and not a short, then surely the whole ESP wouldn’t work and I would get a dash warning light. Sorry for the long-winded waffle, but I’m just hoping my unique symptoms (C1140 code with no dash light) might be recognised by someone before I go further. I noticed Woolly made a fair few contributions to the R171 posts so here’s hoping he might see this. My car is a 2002 SLK 320 with 138,000km on the clock. I’ve had this code since my first Carsoft scan. It drives really tight. It’s a fantastic car with very few of the common problems. The battery has always performed faultlessly (even when I’ve left the interior light on all night). Thanks, Tony Status Not open for further replies. #1 · Jan 30, 2015 Fresh on the success of my P0410 fix (secondary air injection) which turned out to be the K40 (I’m dead chuffed after some of the horror stories I’ve read), I thought I might tackle my longest standing code. I have researched my C1140 to death. I found several posts on this forum, more on the R171 chat, and others on Benzworld.org, particularly the ML section (relevance is debateable). Anyway, I have a C1140 error code, but interestingly NO dash warning light (which all the posts I’ve seen list as a symptom). My investigations list the following as possible faults: 1. Steering angle sensor; open-circuit/short-circuit. Initialisation. This is from my Carsoft, which has proved somewhat unreliable in the past, hence my query to Jeff, the Oracle, who contributed some of the following, 2. B34 ESP brake pressure sensor – electrical fault; 3. Steering angle sensor N49 faulty (unlikely, would cause dash warning light......surely?); 4. Play in steering column causes steering angle sensor to lose memory (unlikely, see below); 5. Wheel alignment; (I don’t think this is a problem – I had the steering alignment checked/adjusted just after I bought the car but before my first Carsoft scan (so I can’t confirm the code was there previously) but the car steers tightly & dead straight and the steering wheel is on the right splines, etc). The code won’t reset – it doesn’t need engine starting or anything like that to come back; it just doesn’t go away. I was so excited when I read about a well-known wiring problem related to a loom being too short (no pun intended), but that seems to be limited to the R171, not the R170. Addressing the above possible faults, I think the first is most likely. I’ve read one post that said no-one on that forum had reported a faulty brake pressure sensor so far, and the others, I would think, would generate a dash warning light. I have had the steering wheel off, only to find the steering angle sensor (clockspring) is a plug-in unit. Obviously the wiring exits the steering column somewhere but I didn’t have time to dismantle the lower dash to find out where. I know the ESP works because the triangle on the dash flashes appropriately (and I’m still facing the right way). I don’t know if the BAS is working (or if it’s related) – but again, no dash warning light. If it is a wiring fault (short) on the steering angle sensor then I’m thinking it can’t be the 12v supplies – permanent and switched - as it would bIow a fuse, it can’t be on the earth wire (well, it wouldn’t make any difference) so it must be on the signal wire to the control unit. I would doubt the steering angle sensor is faulty (because I would think it would cause a dash warning light) but it would be nice to check it. As it’s a plug in unit, and the connector to the brake control module is a multi function plug-in thingy, how do I measure the voltage generated by the steering angle sensor (how do I get the test lead in)? If it’s an open circuit, and not a short, then surely the whole ESP wouldn’t work and I would get a dash warning light. Sorry for the long-winded waffle, but I’m just hoping my unique symptoms (C1140 code with no dash light) might be recognised by someone before I go further. I noticed Woolly made a fair few contributions to the R171 posts so here’s hoping he might see this. My car is a 2002 SLK 320 with 138,000km on the clock. I’ve had this code since my first Carsoft scan. It drives really tight. It’s a fantastic car with very few of the common problems. The battery has always performed faultlessly (even when I’ve left the interior light on all night). Thanks, Tony See less See more Status Not open for further replies. You have insufficient privileges to reply here.

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