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reduced engine power, check engine code p1271

37K views 15 replies 11 participants last post by  dandydon123 
#1 ·
Hey guys,

I have been having problems with the reduced engine light coming on and I finally took it to Autozone to get it check.
The code it read was p1217
They told me it was the accelerator sensor.
Would that be the problem?
I remember awhile back I was pressing the gas and my foot slipped off the gas pedal and the pedal went all the way up with a clunk, that’s when it started so I’m pretty sure it’s the sensor. But I have been reading that people replaced the assembly entirely?

I was also wondering if it is the sensor then where can i buy it for cheap?
Autozone is charging 90 bucks for theirs.
 
#5 ·
Hmm.... The wiring harness? U sure cus I got the code from autozone and printed out the code and it said that it was the accel sensor. But I'll check the wiring too
It wouldn't hurt.

I found the dorman sensor on amazon for 48 bucks.

Thanks for the help guys, hopefully the problem is simple.... ( it never is)
 
#6 ·
A code will not say "the accel sensor is bad". What the PCM does is monitor the changes in voltage from the (2) individual potentiometer signals and compares them. If the signals don't agree or the voltage fluctuates irregularly then a code is set. The Cooling Fan Clutch uses the same PCM reference voltage for its speed detection and a problem with the Fan Clutch harness (or the fan clutch itself) can cause the PCM to think the pedal sensor is the problem.

Many members here have reported that replacing or repairing a Fan Clutch harness fixed this problem for them. That's why you got so many responses that suggested it could be your problem even though at first it doesn't make sense.

I have read a few reports here that the Dorman Pedal assy's do not work well, YMMV.

There has even been reported that the PCM wiring from the pedal to the PCM can be the culprit, you need to troubleshoot more and make sure you buy quality parts.
 
#10 ·
Purchased a Dorman pedal a couple of months ago. worked well while the weather was warm, but as soon as it got cold I started getting check engine light w/ reduced power and code p1217 (accelerator sensor) and pressing the gas pedal did nothing. I have since replaced it with GM OEM and I have not had any issues since. Should of just purchased the OEM one to begin with.
 
#11 · (Edited)
This description is a little lengthy, but I was able to fix the P1271/P1275 problem on my wife's car, and since most forums I have seen seemed to end up with no resolution, with a trip to the junkyard the only solution, I think I may be able to help someone to keep from going crazy with this.
I got the P1271 and P1275 codes on my wife's 2002 GMC Envoy, and after going through all the forums, I still could not get the problem resolved. Several years after we bought the car used, we were going past Corsicana, TX, and got the Reduced power msg. We drove for miles with the car barely moving, but after diconnecting, then reconnecting the battery, I was able to get it running ok again. The car was still under dealer warranty, and the dealer replaced the power control module, but the problem came back a few months later and continued for years.
Several months ago I had to disconnect the connectors on the power control module to replace the valve cover gasket, but a few days later the
p1271 and P1275 errors began happening on a daily basis. I pulled the connectors off again (ALWAYS with the battery disconnected), inspected them, sprayed them with alcohol, put them back on, then off several times, as I used to do in repairing computers, blew them clean with my air compressor, then put them back on. The problem remained.
Finally, despite the warnings on the forums, I purchased the Accelerator pedal sensor from AutoZone ($80 plus), checked out both the old one and the AutoZone one with my needle meter, and the new one was not as smooth as the old one. To check I just put the ohmmeter on different pins on the sensor until I found the 4 configurations for the 2 sensors. You can't check it with a digital meter. You have to watch the needle move smoothly as you press on the pedal. It is the same as checking a throttle position sensor. The sensor arm slides on a circular coil, and if it gets worn, the needle will jump forward and backward erradically as it makes and breaks the connection instead of going up smoothly, and that will trigger the error.
Still I put in the new sensor, but it failed numerous times daily, more than the original sensor. I finally went ahead and bought the shop manual off Ebay, got the pin configurations, and proceeded to test. I tested the +5 volt wires at the accelerator pedal end (white/black +5, brown ground for sensor1, then tan +5 and purple ground for sensor2) using several state-of-the-art safety pins shoved into the holes and got 4.95 volts on each, which was perfect.
The power control module has 3 connectors, but the BLUE connector has the accelerator pedal wires. As the connector is plugged in, pin 1 is at the bottom right, pin 2 is next to it on the right (not across). The thin black plastic cover covering the wires can be popped off with a small screwdriver in case you have to push a pin back out. The connector is held on with just 1 screw, so after disconnecting the battery and pulling the connector back, I proceeded to stick wires into pin 2 and pin 10 to measure the resistance while pressing the accelerator pedal, when I noticed pin 2 was pushed way back into the socket. That appeared to be the problem. So with my handy dandy safety pin I pushed it back in and screwed the connector back in. Two days later my wife got the P1271 error again. So I pulled the connector back off, and the pin was pushed back in again. I stuck a wire into the pins around it with no problem, but the wire would not go into pin 2. The pin was defective. It had to have been defective when it came new from the dealer back in 2002, and the only connection it had was when the male pin was pushing against the female pin because it could not go in. I actually broke the pin trying to force it in, but a quick trip to Radio Shack and a new pin fixed the problem - but only for 2 days. AAAAUUUUUYUGGGGHHHGH!
Then removing the connector I ohmed out the wires going to the accelerator pedal while pushing in the pedal, and the needle on the meter jumped up and down like crazy. How could it have gone bad so soon? I put my meter back on the old pedal sensor, which appeared to be perfect, then took the new sensor out and put the old one back in. I then rechecked the new one I just took out, and it was normal again, though clearly not as smooth as the original OEM sensor. I have seen this occur many times when working on switches and circuit boards in computers. If you get the switch or board too tight, it warps and becomes erratic or doesn't work at all. So I made sure the old one I put back in was not screwed in too tight, rechecked it with my ohmmeter after it was installed, and it was still perfect. Also the accelerator pedal switch protrudes on both sides where the pedal swivels, so the metal mount in the car has a hole in it where the sensor protrudes, but the hole does not seem to match the sensor very well, so it could apply unneeded pressure if it does not line up.
Three weeks later with no errors and having clearly identified and resolving several problems leads me to believe the problem is fixed.
In summary:
(1) The original cause of the problem was a defective pin in the BLUE connector on the power control module.
(2) When replacing the original OEM sensor with the new Radio Shack sensor, I introduced a new problem. The new sensor was not as smooth as the OEM sensor.
(3) When I put in the new sensor, I got it too tight, and although it worked fairly well outside the car, it was very erratic in the car, and that caused the problem to continue. You have to recheck it in the car after it has been tightened down or you may just make the problem worse. Also the hole in the metal mount may not have lined up with the protrusion on the sensor, causing it to warp. Maybe a metal washer placed on each of the 3 screws between the the sensor and the metal mount would have moved the sensor out far enough so a misaligned hole would not have caused the sensor to warp.

In any case, mine is FIXED! Hope this bit of nerve-wracking info helps someone.
 
#13 ·
Im AGGRAVATED!!!. I have done everything to this vehichle. It started with the reduced engine power light. Transmission went bad(replaced), new starter, new battery, new throttle body, new pedal position sensor, new CAT, new thermostat, all new spark plugs and one new coil pack. All of this with 1 months time cause it all seem to go wrong at once or one thing caused the next. And to top it off still getting the P1271 code. As a female I admit that I have been taken advantage of and refuse to put another dime in this vehicle. My last option was to check the wiring to the pedal and throttle body. Looks OK cause im unsure of what im looking for. I hate looking for these these things cause i have to take the battery loose and Im sooo scared to do so and when i do the water squirt me from the headlights which scared the crap outa me when i reconnect Lol. I cant drive this thing a quarter of a mile without the REP light coming on. I have to go in N, turn the car off, on, then back in drive just to make it only a few feet then repeats. Im frustrasted as what to do next. I dont know who to take it to cause im afraid of them overcharging me as im sure they have done before.:thx
 
#14 · (Edited)
For jelainaclark22,
Well, 5 weeks after I replaced the defective pin in the power control connector in my wife's 2002 GMC Envoy and reinstalled the accelerator pedal assembly correctly (not too tight), the p1271/p1275 error has not come back. I think it is very unlikely that your car's connector would have the pushed pin problem, though "unlikely" seems to come back all too often. I would guess that the problem is still at the accelerator pedal assembly. The mechanic may have screwed it in too tight, causing the new one to fail. You would need a multimeter (needle type) to check the accelerator pedal wires at the connector by the gas pedal under the dash. You can get one at Radio Shack if you can find a store that has not closed yet (also at Lowes). Cheap compared to getting it worked on again. You will also need to be half made of rubber to be able to even reach it. I pushed the front seat all the way back and scrunched down in front of it. For testing I just used 2 safety pins, sticking them into the connector where the wires went in. I then used 2 alligator clips attached to the safety pins on one end and the meter probes on the other. You can check the voltage by attaching the positive (red meter lead) to one safety pin and the black meter lead to the other. If the needle goes backward, reverse the leads.
Check the voltage with the ignition turned on (engine not running). With the meter set to read DC voltages, voltage should be between about 4.9 volts and 5.1 volts. You check the voltage in 2 places. (1) between the white/black wire and the purple wire, (2) between the tan wire and the brown wire. You can actually use either a digital or a needle meter to check voltages.
Then check the sensor resistance (there are 2 sensors) with the engine turned off and the meter set to read resistance. You check the resistance in 4 places. (1) Dark blue wire and white/black wire, (2) dark blue wire and purple wire, (3) Light blue wire and tan wire, (4) Light blue wire and brown wire. Here it doesn't matter which wire you connect to the red or black meter probe, just check the 2 wires in each step together. When you press the accelerator pedal down, the needle should move up or down smoothly, should not jump or hesitate at all, as that will generate the error code. You need a needle meter for this.

If you want to try a quick fix (or you got erratic needle movement in the previous tests), you can just loosen the 3 hex screws attaching the accelerator pedal assembly to the mount a few turns to relieve the pressure to see if the error goes away. The top screw is not easy to reach with a socket, so I used a wrench. These are metric. Also my accelerator pedal from AutoZone tested a little erratically, so the new one could be defective.
By the way, I am not knocking Autozone. My car is now mostly made up of parts from Autozone or OReilly.

Also if you are not built like Spider Man and can't get to the accelerator pedal assembly easily, you can disconnect the battery (just need to remove the negative terminal) and use a small socket to remove the screw in the center of the power control connector. There are 3 connectors colored white, gray, and blue. You need to remove the blue one closest to the firewall (It is about 2 inches from the brake fluid reservoir). Pull it away from the power control module, and check for any pins pushed back into the connector. Focus on the pins at the lower right. I used a bright light and 2 pairs of glasses for magnification. It would be a real coincidence to find a pushed pin there, though not impossible. Make sure you put the connector back on straight. ALWAYS MAKE SURE THE BATTERY IS DISCONNECTED WHEN PLAYING WITH THESE CONNECTORS.

Also don't assume the mechanic is aware of the problem of getting the accelerator pedal assembly too tight. I haven't seen this addressed in any of the forums, but I absolutely verified the problem with my meter and have seen it often when working on computers.
I hope I did not overwhelm you with this. If you don't feel comfortable doing these checks, maybe you know someone who can check it for you - maybe Peter Parker (Spiderman)?
 
#15 ·
If you have no power when to try to accelerate, this would mean no fuel is getting to the intake, I am not saying that the wiring harness sis not a problem but it would not prevent you to accelerate. Do a search on reduced power and limping home, change the accelerator sensor, weather it be $90.00 or $150.00. You could end up paying that much changing all kinds or part just to come back and change the sensor anyway.:m2:
 
#16 · (Edited)
I don't see P1217 in any of my manuals. You must mean P1271 - "Excessive voltage difference between Accelerator Pedal Position (APP) sensor 1 and 2". There are 2 sensors in the unit so if one goes bad, you can still limp home on the other with the service engine light on. As I mentioned in my previous posts, I got a replacement sensor from Autozone for $80.00+, but it turned out to be flakier than the original (my original problem turned out to be a pushed pin in the connector to the power control module, and I put my original sensor back in). If you have a needle type multimeter, you can test the accelerator pedal sensor in the car as described above, or you can take it out and connect 2 of the pins together until you see the needle move, then push the accelerator pedal down and up slowly to see if the needle moves smoothly. Alligator clips work ok for this. There are 4 different ways to connect 2 pins together (1) sensor1 to 5v,(2)sensor1 to ground, (3)sensor2 to 5v, (4)sensor2 to ground. You just have to play around to find them. 2 ways make the needle go up, 2 make the needle go down. All 4 must make the needle move smoothly to avoid the P1271 and P1275 error codes. The codes can be erratic in the car, but you can see them easily with the meter. If the needle stops or jumps back and forth while you are pressing the pedal down slowly, it is bad. Also, as mentioned above, the sensors can test perfectly out of the car, but if you tighten the 3 screws in the sensor assenmbly too much, it can bend the sensor case and make it erratic in the car so that it fails. That's how I diagnosed my problem and how I fixed it.
 
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